I like brimstone a lot to, but yeah you are right, i don't really use the stim beacon.
Stim beacon is hard to use, the circle around it is huge, so a lot of the time's the enemy can take advantage of it aswell.
And second, spraying in this game isn't really worth it 99% of the time..
I would vote that they replace the stim beacon with something that is more usefull in more cases.
But the smokes are very strong to defend positions.
I don't use incendiary alot either.. i think it dissapears far to fast to be effective.