I think they are stupid for higher levels :)

What I have observed is that once I have hit 29 or so, the quest pretty much gives me as much as the valor for the level bracket before - but charges 50s instead of 30s!

Valor of 600-700 could be obtained by doing 2 or 3 battles which usually amount to 20-30s! So, the valor quest aint anything good for this bracket.

I would suggest for an increment in the valor benefit.