And true, you could play in drafts which are nice because they put everyone on the same level playing field, but you're still paying $15 to buy more cards when you already have cards at home
What sets Phage the Untouchable back is that its going to be hard to achieve this most of the time
Black Knight is great against Blue/White Control, Mono White, and any other deck that relies on Swords to Plowshares, Wrath of God, and Balance for creature removal (under Alpha rules, protection from white makes Black Knight immune to Wrath of God and Balance)
Since dashing is still casting the spell just for a different cost, you still add the appropriate commander tax onto the cost that you pay when you dash based on how many times you already cast the commander
Even if one of the cards gets removed, you can get access to the combo right away again since they'll just go to the command zone to cast again later