Dawn Charm is just too versatile to be ignored. It's a Fog (or Holy Day) against an alpha strike, a regeneration against a surprise pump/board wipe, and a counter against any pesky kill/bounce/tuck effects. With equip/voltron you're kinda centered on one or two key cards, keeping them alive is key.
Cards discarded by ~ are exiled.
t, discard a card: Draw a card and put a charge counter on ~
When ~ has X charge counters on it, flip it.
~ has protection from the card types exiled by it.
~'s power and toughness are equal to the amount of card types exiled by it.
I made a Maralen of the Mornsong deck that uses Neverending Torment. I know it's not great but it's budget and fun to play for the first few times. Especially when they don't do anything about the general or you're not playing against blue. The deck is here.
It's unlikely you're going to mill anybody out with it, and blind milling is statistically just as likely to get them closer to a threat or an answer as it is to eliminate it. Add to this the fact that most EDH decks run recursion, and I'm not seeing how "its ability is too amazing to deny."
If I'm missing something, prove me wrong, but I think that Mindcrank is a card with a few narrow combo applications and very little else.
I guess it's more that I run lots of grave recursion, that I find it easier to use, but it makes players have a difficult time in setting up top decks and preparing their answers when they're getting milled early game. Also there's just as good of a chance that you hit their answers as there is of letting them get to them.
You're right it'll never mill someone out completely, unless some infinite damage combo is pulled (in that case it wouldn't matter though), but a few hits from an aggro deck can start to make people cry, as does paying ones own life. Sylvan Library and Necropotence become terrible.
It can come out relatively fast, turn 1 Sol Ring or worse case turn 2, and it's typically not a huge threat in early game where the beats are far a fewer apart, but it grows with potential for the rest of the game.
It looks good for comboing off, but without tutors in your hand or your mana excel to play maralen any earlier it will take 3 turns for her to come out. Against blue you fetch Boseiju turn 4, and turn 5 you fetch Ad Nauseam. That means that it's only turn 6 that you get all the cards in your hand you should run Reliquary Tower.
I get that this is a fun deck I run one that's almost the same here. The problem i that this deck won't work if someone knows what's going to happen. It's fun to pull off, once.
EDIT: Also I forgot to mention, you should try and keep the combined converted mana cost as low as possible, the more damage you take the more vulnerable you are. You have 40 life to be spent in 6 turns. You shouldn't waste a drop of it
I agree with KirkSauce, the amount of power G/W has at it's disposal is incredible. Green itself is comparative to blue in terms of strength in Commander and with the backup of white it can be very competitive. Rhys relies on two things, mana production, something Green can handle very efficiently, and tokens, without them his abilities are meaningless. With that said, he has a great supply of cards that fit so well in this deck.
A brief list of good cards that work well with Rhys: