The Boiler is:
-Tier 3 xeno
-Dedicated long-range artillery for xenos
-Keystone in any xeno stationary warfare situation
-Really fucking annoying to play against
Boiler's the top support xeno. It's not self-sufficient, it can't help xenos outside of combat, but its combat support abilities are priceless.
Maybe even too much.
Recently, the issue of boilers being absolutely crucial and obnoxiously hard to deal with properly have been highlighted with the addition of mutators and weapon rebalancing.
There's just so much a gas of murder brings for the xenos that any marine push that requires passing a chokepoint grinds to a halt when a boiler is supporting the frontline, when the frontliners would slowly give ground to the push in exchange of casualties. Two boilers at a chokepoint can completely lock it down with no chance of pushing, barring excellent timing for OB, CAS, or sniper suppressing the boilers with incendiary bullets. The last is unlikely to happen with mutators giving a larger buffer for boilers to tank before needing to retreat to heal.
Personally, I feel that the boiler has far too much utility and ability to control the battlefield with no reliable counterplay on marine part. OB is too slow to fire and reload, snipers are less-than-lethal when the boilers have even minimal tanking support. CAS can work wonders, but it relies a lot on communications and timing, and isn't anywhere close to guaranteed to kill.
In short, there are too many counterplays for boiler counters.
And on top of this all, mutators allow boilers to survive what would have killed them before, and the last but not least, Wider Gas exists, absolutely nullifying multi-layered defenses by spreading gas further than ever before.
What should be done is increase the recharge time for boiler gas clouds considerably. Currently there is only a short window to push after the gas dissipates, which is functionally none when there are two boilers. While it may be possible to push through a chokepoint into an open area in the lull, if the chokepoint is either a moderately long tunnel, such as certain LV locations, or there is a large amount of sticky resin, the push is doomed to fail.
For marines, this is extremely frustrating, since you can't usually even see what's firing at you, and if you can, chances are that it's just about to fire a gas cloud behind you and you're about to get mobbed by several xenos.
For xenos, a support this effective is unhealthy for the game in general, since any major pushes and defenses have to rely on the gas cover to work.
TL;DR nerf boilers