The thing is that you can't
really call the colors different "factions", Erik.
"Factions" implies that the card pool has cards that are unique to your "faction" — if you're playing a Druid in Hearthstone, you get Druid cards that no-one else gets to play with and there are Mage cards that you don't get to play with. If the dev team forgets to stick some key effect in the Druid pool or the Neutral pool, I don't get to use that effect in my Druid deck, and there's nothing I can do about that. If I want to be able to Wharglbargl (an effect that the devs
foolishly only gave to Shamans), I don't get to play with Druid cards.
In Magic, on the other hand, you can have
any number of colors in a deck. As a result, having individual colors be incapable of dealing with certain situations is more about
texture and
trade-offs than it is about having gaping holes in your strategy. Sure, Red can't
natively deal with Enchantments, but nothing stops you from splashing into White/Black/Green and tossing the appropriate answer into your deck (or trusting that your fast, consistent mono-Red deck can just go
under the Enchantments). The game is implicitly designed around color pairs/triples, and as of TBD
every pair is capable of dealing with every card type in one way or another.
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As a digression about Blue being able to do "anything"... yes and no. While Blue's card pool can
theoretically deal with anything, its removal is actually
really bad — counterspells are your only
real form of 1-for-1 removal, with bounce and polymorph effects being natively 0-for-1s. And counterspells have the built-in drawback that their timing is
hyper restrictive, since you have to have them
before your opponent plays their threat.
And, sure, there are quite a few Blue cards that break those rules... but if we go by color-pie breaks
Red has enchantment removal. And, hey, as Cube designers? We can just straight-up exclude those mistakes from our cubes.