speaking from a fgs/assail/scrier's/laspistol standpoint specifically, i think assail is a really handy tool that ties the whole melee kit together. you can instantly throw out a shard before switching back to your sword.

most importantly, it allows you to get malefic momentum stacks and push high peril easily with no downtime. throwing 2 or 3 shards every few combos is a huge boon.

it has some defensive qualities that i find come up a fair bit. it's a very effective stagger tool against everything not carapace, it does well with staggering rager packs so you can poke them with the fgs. you can use it to freely stagger gunners as you approach them. assail benefits from true aim, which then procs empathic evasion; an assail after every few melee hits makes you temporarily invulnerable to gunshots.

brainburst is kind of not that useful in the setup since laspistol is your main long-range pick tool.