No need to raise collective - if you have been using more than 50% Tq with 2 engines, then when one fails, the other will ramp up to try to provide more than 100% Tq by itself.
The OEI limits might be 135% or even a bit more for 30 seconds to get yourself to a speed range where you can use less than 100%, or perhaps to cushion onto the ground. Often this would require you to reduce collective on engine failure, particularly if you have been in a 75% twin cruise, and the single engine is now trying to put out 150%.