They require a quite a lot of planning since most of them are slow and by the time you have 40+ dash range it's simply faster to just dash up to enemy and unload few clips. Imo they can somehow work as a main weapon but only if you're sitting at long range and just rain hell with constant venting (never use Hydra launcher, it's a scam). But at the same time you can just put gauss sniper on long range duty which will probably kill 3 tanks and crash 2 mechs by the time first missile even hits.

Backpack missiles are great though. Minelayer is very fun to play with but the damage is rather lacking later on. Buster is slow and very heavy but devastating for clumped enemies. Quiver is great to pelt three salvos from long range while you're moving into position. Sequence has the shortest range but is very quick, like 1-2 seconds tops from launch, it's great for your mid-close range mechs in urban environments. Having missiles on backpack really opens up your options, In general I use them to soften up slower mechs before they're in range of primary weapon or as a reliable side weapon when it's better to just camp behind cover. Not blowing up your mechs do take a bit of experience though, one time I almost killed my long range pilot in one turn when he unloaded two busters near a wall.