It kind of depends on how many points you are "wasting" not taking advantage of Arsenal 2. Perhaps the harpoon is the way to go and just use it when you get the opportunity?
I think the T-47 might actually be better against other Rebel lists than against Imperials lists. Impact is wasted on everything on the Imperial side except the AT-ST at the moment and the Harpoon only works against AT-STs and AT-RTs thanks to Cover 1 on the repulsor vehicles.