So many hero builds don't include interrupts...why?

I run interrupts sometimes, good way to beat multihealer groups or nukers.

Because pain inverter can't kill them if they get interrupted.

P.S.: EVAS works great on that bar too. You do't have to choose.

Basic answer? Because it's easier to prot/heal the damage in PvE then keep it from happening in the first place. damage occurs at such a high rate in normal PvE that interrupting one or two skills isn't going to make or break anything. Exceptions are Tease/Cry of Frustration

In PvP, it's easier to prevent and interrupt the damage then to heal/prot it more often then not