I guess I have a dissenting opinion: the decimator really doesn't seem very good. It goes down fast and is a crit sponge.
I just finished a game where I played rebels. I went head on with E'tahn against the decimator - so his attack had one guaranteed crit. Behind him I had two Y-wings (dutch+gold) with the BTL title and ion turrets which were also issuing crits (on primary attack) via E'tahns ability, and way off to the side I had Dash + Mercenary Copilot + HLC issuing two crits via mercenary copilot and E'tahns ability. (and 5 attack dice thanks to Jan's HWK) After the first round the decimator had several crits including one that reduced its attack to 2 dice.
. I play 200 point games: maybe it's less viable in higher point games.
200 point games.. then your opponent could have 4 decis!!