While the goal will always be that 0.5 card OTK, itd be foolish not to have a few redundancies built in
I think your concerns are valid
I mean, considering all the effort you have to go through to get Rainbow Dragon out(who is already a pain to Summon), in addition to a Tuner who is useless outside of 2(well, 3, since This card) cards, you should give the player a decent reward for going to such extremes
The rest of the ratios look good, though I would prefer another board wipe or two: board wipes are good because your early turns are spent ramping, not developing a board presence, so a board wipe is a great catchup mechanic before you start dropping your haymakers
Fortunately for you and unfortunately for your opponents, because Blightsteel Colossus is indestructible, if they dont have an exile card, a creature 11 power or greater, or a horde of creature tokens with a total power of exactly 11, the game is done