As far as I now when one engine failure occur on twin engine helicopter the procedure is to apply collective up to get max power from the other engine.
Why should you do that?
You adjust the collective to maintain a safe Rrpm. In a high speed cruise the power normally demanded may be higher than one engine can provide so the collective would be lowered to maintain Rrpm. Should it happen at a speed range where the remaining engine can contain it then leave the collective alone.