Other possibilities include the Fantastic Four or a set focused on the cosmic side of the Marvel universe
If youre designing for print, think in trim, bleed, and safe area (because printers love cutting off the one thing you cared about)
In general, when looking at power level, I considered the overall game plan, the synergy of the 99 with that game plan, things like interaction, ramp, mana base and card draw, the commander, and the power of the remaining stand-alone cards
If you are comparing him with any casting cost, then Wild Mongrel just whoops him in a race
Borne Upon a Wind Borne Upon a Wind will take your broken combo piece and toss it onto the battlefield whenever you like
You can then pay one mana to either remove a counter from a Creature you control to make a 1/1 Saproling, or sacrifice a Creature to put a +1/+1 on a Creature