Wither pingers are very handy at taking out specific creatures when they hit the board. That's really the only reason to have them. A couple of Viridian Longbows usually will do the trick if you want them.
Also how are you removing -1/-1 counters from your creatures? Soul Snuffers is great but also takes out your smaller creatures. This might not be a concern just thought I would mention it.
Here is an interesting thought. Have you thought about switching out the Grim Poppets for Skinrender? And throwing in a couple of Cloudstone Curios? It would be cool to bounce out creatures that have too many counters on them so they wouldn't die. You could play Skinrender bounce Soul Snuffers and keep doing that until you wipe the board. The go in for the kill.
Also as a suggestion I would go the Crumbling Ashes route rather than the Necroskitter route. The main reason is that you are using 2 colors so CA's casting cost is more multicolor friendly. Also it comes out 1 turn faster. It doesn't matter in the long run if you are playing mid-range, but if you want to hurt them fast I would go CA.
Oh and by the way Corrosive Mentor > Everlasting Torment. I play tested both and found that ET would sometimes screw me if my opponent pulled out pingers or something that could deal direct damage.
Remember: Playing a game according to the rules keeps it fun for everyone. If you played monopoly and every time you passed go you make up a rule that everyone had to pay you $200 sure the game would be fun for you but suck for others.
There is a difference between being a rulebook thumper and following basic card text in the game. Do not bend on the rules if you are sure about them. Also if it is card rulings that seem to cause you the most problems there is a fantastic Iphone Application called "MTG Guide" that allows you to look up specific cards and see all rulings for that card. The Kjeldoran Dead example stated above is in there.
If you allow your friend to continue to play by "his" rules you really aren't help him be a better player. You are being an enabler. Explain the correct rules to him. If he doesn't listen ask the question on the rules forum. If he still refuses take him to a magic store near you for FNM. I'm sure there will be a lot of players there that will set him straight and not be as nice about it as you are.
You know I was thinking about this myself. The fact that each point of damage gives you a poison counter I feel is kind of broken as well. Especially because there is no real effective way of removing poison counters from yourself. The only thing I can think of is Aethersnap and I'm pretty sure that doesn't even work!
Hold on! In your post it says you are trying to make a WW deck with another color. Is the WW white weenie? If that is the case then I would venture to say White/Green is a better color combination for weenie.
My friends and I have a house rule where if you don't like your opening hand you can redraw it once and you have to take it unless it is 0 or 7 mana. Possibly as a result I ran to few mana in my decks as once I posted them up on here one of the first things people said was increase the mana. Obviously I was wrong and incorrectly biased because of my house rule so I would say add a few extra mana and it probably will be good.
This is the exact house rule we use! Free mulligans if you don't have at least 2 mana is awesome though! Lucky you!
You can do it a lot of ways. Search the forums and you will find a marketplace discussion that describes all the places to buy cards. You can find them anywhere now. Amazon, Walmart (precons), Ebay, or my favorite Starcitygames.com. There are lots of places to buy from.
Between the Eldrazi Monument and Knight Exemplar you should be good on the Anarchy. If land destruction is big in your group you might want to consider Sacred Ground which is cheap. You can keep it in your side board if you don't want to main it.
There is also the grand old Crucible of Worlds. Either one of those would help against flash fires.
I hope you don't think people on this forum are attacking you or your deck. This game is fun and should stay that way. You came on the forum and asked for opinions so people gave them to you. If you have a favorite card or something you feel you can not live without than do not change it. Your meta could be different from everyone else's. Keep what you want.
On your comment about Harm's Way. If you are looking for a good replacement consider things outside of Knights (i.e. Intrepid Hero)or something simple like Ghostly Prison? It doesn't directly save you but with a couple of these out it becomes very difficult for your buddy with a bunch of huge flyers to attack you easily. Also consider putting in utility lands like Maze of Ith or the cheaper version Kor Haven which also gives you mana.
Remember...these are all just suggestions. Take what you think is good and leave the rest.
EDIT: Sorry for the edit but I did a little research. If you are looking for a white spell that redirects damage from your creatures to theirs consider Kor Chant which will redirect all of the damage instead of 2.
I'm not sure if you are keeping this in standard-casual format. If so my suggestions might have to be thrown out of the window.
Consider some of the following (I'm basically spitting out card names that are in my blue/white flyer deck: Fog Bank Wall of Denial Pride of the Clouds - The most bada** underused flyer ever. Krovikan Mist Shapesharer - good to get rid of big legends and double up PotC stated above. Also pumps up Krovikan Mist Serra Avenger
Holy crap! Don't forget Capsize which by far has to be one of the best if not the best common in tempest. Also you could use Legacy's Allure and Legerdemain to jack their creatures. Hmm...what else might be fun in mono blue...Propaganda and Stinging Licid are kind of neat. You might have to go 2 or 3 colors to get to 60 cards effectively. Splashing black might not be bad. [c]Dauthi Embrace[c] and a lot of other "dauthis" were in tempest.
EDIT: Yes that was a stupid question...no pariah.
Also how are you removing -1/-1 counters from your creatures? Soul Snuffers is great but also takes out your smaller creatures. This might not be a concern just thought I would mention it.
Here is an interesting thought. Have you thought about switching out the Grim Poppets for Skinrender? And throwing in a couple of Cloudstone Curios? It would be cool to bounce out creatures that have too many counters on them so they wouldn't die. You could play Skinrender bounce Soul Snuffers and keep doing that until you wipe the board. The go in for the kill.
Also as a suggestion I would go the Crumbling Ashes route rather than the Necroskitter route. The main reason is that you are using 2 colors so CA's casting cost is more multicolor friendly. Also it comes out 1 turn faster. It doesn't matter in the long run if you are playing mid-range, but if you want to hurt them fast I would go CA.
Oh and by the way Corrosive Mentor > Everlasting Torment. I play tested both and found that ET would sometimes screw me if my opponent pulled out pingers or something that could deal direct damage.
There is a difference between being a rulebook thumper and following basic card text in the game. Do not bend on the rules if you are sure about them. Also if it is card rulings that seem to cause you the most problems there is a fantastic Iphone Application called "MTG Guide" that allows you to look up specific cards and see all rulings for that card. The Kjeldoran Dead example stated above is in there.
If you allow your friend to continue to play by "his" rules you really aren't help him be a better player. You are being an enabler. Explain the correct rules to him. If he doesn't listen ask the question on the rules forum. If he still refuses take him to a magic store near you for FNM. I'm sure there will be a lot of players there that will set him straight and not be as nice about it as you are.
+4 Akroma's Vengeance?
Extra cycling with a similar if not better effect.
Although it could potentially get rid of your Astral Slide
Leeches works but hurts you in the process.
This is the exact house rule we use! Free mulligans if you don't have at least 2 mana is awesome though! Lucky you!
There is also the grand old Crucible of Worlds. Either one of those would help against flash fires.
I hope you don't think people on this forum are attacking you or your deck. This game is fun and should stay that way. You came on the forum and asked for opinions so people gave them to you. If you have a favorite card or something you feel you can not live without than do not change it. Your meta could be different from everyone else's. Keep what you want.
On your comment about Harm's Way. If you are looking for a good replacement consider things outside of Knights (i.e. Intrepid Hero)or something simple like Ghostly Prison? It doesn't directly save you but with a couple of these out it becomes very difficult for your buddy with a bunch of huge flyers to attack you easily. Also consider putting in utility lands like Maze of Ith or the cheaper version Kor Haven which also gives you mana.
Remember...these are all just suggestions. Take what you think is good and leave the rest.
EDIT: Sorry for the edit but I did a little research. If you are looking for a white spell that redirects damage from your creatures to theirs consider Kor Chant which will redirect all of the damage instead of 2.
Consider some of the following (I'm basically spitting out card names that are in my blue/white flyer deck:
Fog Bank
Wall of Denial
Pride of the Clouds - The most bada** underused flyer ever.
Krovikan Mist
Shapesharer - good to get rid of big legends and double up PotC stated above. Also pumps up Krovikan Mist
Serra Avenger