Hey guys, my merc is only level 35 and I've been playing as Pyrotech up until this point, my question is as Arsenal do I only want to rail shot with 5 stacks of tracer lock? Thanks

Generally, yeah. If you're in a hairy situation where you can't get that many Tracer Missiles off (on the move, having to off-heal to keep a tank alive, getting interrupted a lot), go ahead and use it with 2 or 4 stacks. It's cheap and hard-hitting, so you don't want to delay it a whole ten seconds just to get that extra stack or three. Ideally you should have more than enough time to get those three Tracers off before it comes back off cooldown, but play it by ear if things get messy.

Generally, yeah. If you're in a hairy situation where you can't get that many Tracer Missiles off (on the move, having to off-heal to keep a tank alive, getting interrupted a lot), go ahead and use it with 2 or 4 stacks. It's cheap and hard-hitting, so you don't want to delay it a whole ten seconds just to get that extra stack or three. Ideally you should have more than enough time to get those three Tracers off before it comes back off cooldown, but play it by ear if things get messy.

pretty much this. also, if you are in pvp and need to finish someone off at a distance.

example: they are 10+ meters away, you need a decently hard hitting move to to kill them and HSM is on CD.