I've always thought delegating a lot of HP is not really helping others out. I would rather have a bigger share to show more of influence with my upvote.
Now I will be delegating about 20% of my HP here soon to a community I will heading up. I think that will be good as I will be upvoting from there. I won't move it yet though until I put it into motion.
I kind of agree with your percentage for delegations... I try to do similar, but around a 10-15% delegating out...
Everything more than that is damaging my friends and community, and the decentralized nature of HIVE