Pegasus is in-element with Blessing. +3 atk from blessing means +6 damage from dive. So, it is balanced and actually a pretty effective attacker in / decks, manytimes even better than Wyrm.
Arthan, blessing is exceptional with many creatures, minor vampire. otyugh, scorpions in general, for duo + light air, I personally prefer to use Morningstar + flyweapon, with shard of wisdom, and perhaps complete skyblitz (yummy!!). but I agree that a duo pegasus in air-light can be better wyrn, it would save air for better purposes.
Skyblitz targets all airborne creatures on your side of the field, and morningstars are immune to targeting.
Shards: the game is a real problem that people are trying to come up with a fix for, with SoW being an offender for providing more attack then other buffs for the same or less cost, on creatures who don't need hp anymore. Rather then buffing all other options to be as good as on overpowered card, it might make more sense to
nerf the overpowered card.
The one problem I see with pegasus is that is a forced combo with blessing. Without using some sort of buff, it ends up being underpowered (at least when unupped). Using any other buff requires a trio. So other buffs get used with wyrm (making it a duo) while pegasus is only ever used with blessing.
Pegasus, cause 12 damage, ok
But still loses to frog with adrenaline 12 damage with only 6 total, and need not be dual.
Frog + adrenaline is very cost efficient, but that is because it requires an exact match. If you get a weird draw of 1 frog and 5 adrenaline, you have 12 damage. If you get a weird draw of 1 pegasus and 5 blessings, you have 36 damage (the same as if you had a balanced draw). Adrenaline is also much weaker against most shields. Blessing provides resistance to damage based CC, while adrenaline provides resistance to freeze/delay. Thus, each combo has significant benefits over the other, and which to use seems more a question of style and meta-game than power.