Make us invulnerable during LB animation lock?

[Rufalus]

being immune to all damage while casting it would cause people to cast it during attacks and then cancel mid-cast...

I meant you're only invulnerable once the attack is locked in and can no longer be cancelled, I'm not asking for something stupid and game-breaky.

Aren't you supposed to pick the appropriate time to do it?

That's what people adapted to, but I am asking you to think about it, is that design a good one. What about a battle with no downtime when it's never safe to locked down for a long animation. Should your ultimate attack really have a huge downside that limits its use.