Sorry @bansa , by bringing up Dark Pact, I shifted the discussion away from your legitimate complaint about Birds’ Nest. I apologize for that.
I completely agree that Birds’ Nest is a very strong card. Its appeal IMO is how consistent and low-risk it is, even relative to other A-grade spells like Bloodlust, Kidnapping, Lich’s Bargain, Temporal Distortion, etc. It’s cheap, there’s no obvious way to play around it, it doesn’t put your base or economy at risk, and you don’t need another card in hand or on board to play it. In these respects I’d say it’s only second to Dark Pact.
However, Birds’ Nest does have some drawbacks. As Shadow_Night_Black pointed out, it’s slow: what you get is 2 evasive damage per turn, starting next turn. This can add up to a lot, but it’s nowhere near the immediate pressure that some other cards can generate.
Moreover, Birds’ Nest has a hard cap: you can’t spam it turn after turn and get an endless stream of cards, or a bigger and bigger army, or whatever unit you want from your codex turn after turn, etc. You get two 1/1 Birds and that’s it.
Granted, you can make up for both of these drawbacks with combo pieces, and Birds’ Nest does have amazing combo potential with stuff like Spartners and Two Step. This is also what sets Birds apart from other early game fliers. But that just means Birds’ Nest is a key component in some strong game plans, not that it’s necessarily too strong as a standalone card.
All that being said, the list of changes EricF proposed here, and which we might test during the next tournament, does include a nerf to Birds’ Nest - basically making it even slower than it is. Another option I could think of would be making the Birds untargetable by Buff spells, similar to Nullcraft, which would limit their combo potential.