1. Power Surge only works with Jump and Spineshatter Dive
2. DoTs are dependent on your base 100% Potency and readjust accordingly Example: Say you have Heavy Thrust+Blood For Blood+Disembowel up, then your base should be 155 percent potency (Blood For Blood + 30%, Heavy Thrust + 15% Disembowel + 10% Pierce) With Chaos thrust and Phlebotomize ticking they tick at 25% (Phlebotomize) and 30% (Chaos) of the base of 155%.
3. No it's never ok to let any of your DoTs or dmg buffs fall off.