If you're using high gain, I would suggest you consider the rack version of the decimator. The signal out of the pre-amp lacks the dynamics of the signal coming from the guitar, so it's much harder for the gate to decide when you actually want it to come in. The rack version (ProRackG) does the job of gating at the amp input and in the loop, but does both based on the signal going in to the amp, carrying all of the dynamics of the guitar signal.
Obviously it is a fair bit pricier, but of all of the gear I've bought it's one of my favourites as it does the job incredibly well, has an excellent response time, and is totally transparent.