Generally I'd say shoot for a plateau like 10% (that's the extra UA tick). There isn't another plateau for a while after (unless you count an extra BoA tick but that's pretty useless). So until a couple tiers from now when you can push for 30% (for another extra UA tick) or even.. 25%? (not sure) for an extra corruption tick, your best bet is to stick with 10%.
Now, remember that totems can be knocked down DI is dispelled constantly (although it can be reapplied it just takes a global) so unless your situational awareness is incredible I'd shoot for 10% before buffs.
Going above that isn't going to hurt you, but it will only make Fears, Haunts, and GCDs faster, it won't increase dot tick speed until you hit another plateau.