Yeah, I get that although I just noticed that Portable Hole says permanent instead of creature. Being able to kill cards like Bonesplitter, Rancor or Coldsteel Heart makes it much better. Seems reasonable in a cube with de-powered removal (although depends on how de-powered).
Portable Hole is hardly tier 1 removal, but I also wouldn't raise an eyebrow if I saw it in a list. Worse creature removal than Fatal Push but more versatile and has artifact synergy which may eventually be relevant (probably more than the "warriors" theme some people seem to care about lmao)
I recently cut Sunlance and I think that is a good comparison to Portable Hole, particularly in number of targets. Portable Hole hits about a dozen more cards in my 512 card Cube, considering that Hole deals with some tokens a little bit better like 1/1 white Birds and 1/1 white Spirits, but specifically the tokens from Feudkiller's Verdict and Roar of the Wurm. The other obvious point is that Portable Hole hits almost all of my mana rocks, which means a lot to me. There are also a lot of other relevant non-creature permanents, like both Shrines, Sol Ring, Skullclamp, Land Tax, and Sylvan Library.
At this moment, I would probably test Portable Hole. What it lacks in power dealing with more expensive creatures, it makes up for by dealing with those other powerful artifacts and enchantments. I think the real question about Portable Hole is not about how powerful your removal is, but how powerful your threats are.
It probably goes without saying, but Power Word Kill is the best 2-mana removal spell black has. I have 6 misses in my 512 card Cube, compared to 12 for Cast Down, 15 for Go For the Throat, 37 (creatures that have or can get counters) for Heartless Act, 41 for Ultimate Price, and 49 for Doom Blade. I am less on the anti-color hosing bandwagon when it comes to otherwise broadly powerful cards, but I think Doom Blade will be my cut here.
As with anything else in cube, it never goes without saying and is always dependent on the rest of the cube. Power Word Kill has 9 misses in my 400-card cube, compared to 7 misses for Cast Down. On top of that, I kind of hate a card that has to list four conditions as opposed to one - it is convoluted and wordy rather than clean and quick to parse. And the name feels like it belongs in my Un-Cube, not my Peasant Cube. I'll still consider it, but it's not indisputably the best.
So... a peasant cube can now contain 4 different cards that make the big hammer reasonable (this guy, Arden, toll collector, and kor outfitter). If we get more equipment with hefty equip costs, that may be the start of a package.
Taking a look at your list, I did forget a few of the (1) to equip cards (namely Heirloom Blade and Bonesplitter)
I tend to think of Grafted Wargear and potentially Lightning Greaves with regards to equipment.
Still I don't know if a (1) mana rebate is really enough for this guy to shine.
It won’t make my cube, but it’s interesting that this could make other equipment playable. Equipments are mostly evaluated based on the equip cost, and perhaps there are equipment that would go from unplayable to good?
Colossus Hammer becomes 1 mana +10/+10 lose flying, which seems like an insane ceiling.
Personally, I feel that adding subpar equipments just to enable other subpar cards is a strategy that might be fun for one or two drafts, but quickly loses its novelty value as they are cards that would always need to be drafted together or be subpar.
I think it also greatly depends on cube size, since you're less likely to get all the pieces in a draft in a 540 cube than in a 360 cube.
However you can fill your entire Boros guild section with dwarves who care about equipment now, so that's pretty fun and flavourful. (Koll, the Forgemaster, Reyav, Master Smith and now this guy). Could be a fun package, but I don't think the number of actually good equipments warrant such a package in Boros just yet. I don't run the 'broken' equipments (both Warhammers and the Clamp), so that may influence my opinion slightly.
Bruenor also has a pretty nice bonus for your currently equipped creatures too. I think the more interesting approach is in playing the Boros-colored equipment that also fit the curve as a creature. Between Ancestral Blade, Dwarven Hammer, Mask of Immolation, Mortarpod and maybe Valkyrie's Sword, you have a set of equipment that become great creatures with Bruenor and then leave behind great equipment. +3/+1 for 1? +5/+0 and trample for 3?
Not for me. Haste is better than create a treasure, if you don't have an artifact to destroy.
Dawnbringer Cleric is decent:
When etb, choose one: gain 2 life, destroy target enchantment or exile a card from a graveyard.
Understandable. I value the ramp more, but haste is good, too. They're both strictly better mechanically than Manic Vandal, and it's nice to have choices.
Speaking of choices, I agree that Dawnbringer Cleric is decent. It offers graveyard hate and enchantment hate without being too narrow and offers lifegain as a fallback. I think I'm still running Lone Missionary, and this could easily take its place.