Ah, I love not having a reliable access to the internet. Oh well, I'm a boomer and I feel like ranting, so even tho I am late, here goes: Be mindful, I stopped playing somewhere around early july, so take all this with a pinch of salt. Anyways, as always, issue with engineers is the powercreep.
In the before times, FOBs before were broken by the good old combo of boiler gas + queen screech + a rav, and with much less effect, the crusher train. Then engineers got better, and boilers were given strains. The increased gas area started the whole girderpsam thingie, which, if done correctly was very hard to crack. That got nerfed, but the quality of the engineers was good enough to keep pushing the xenos away. The devs reworked the strains and added the railgun boiler, which was surprisingly hated by the community (because it was not that good for "muh unga"), but it was insanely useful at dealing with FOBs, because it was a massive drain of resources. That refusal to use their tools, led to more and more nerfs, changes to maps to make FOBs easier, portacomms, and the addition of spitter acid spit, which was again hated (and the issue of needing insane quantities of water not adressed properly) until it was so bad that it got reworked. And that's where we are:
Now most of engineer leeway and options are gone, and instead we got a LOT of sentries and M56s (much more than it's sensible), and free mortar rounds. And even tho we got some noob traps like the bell, xenos have very little tools to deal with well constructed FOBs. Gas+Queen+Rav doesn't quite work, cause teslas are OP as hell, and stops the queen from screeching/ravs from shielding. So boilers have to be able to basically carpet deny the FOB. Sentries got buffed pretty hard, and now lowly t1s can't get near. Sentinels are the only ones that are somewhat decent at it, since they can stay out of sentry range, but in exchange they are pretty squishy. Crushers are mostly glorified defenders against FOBs if they build them well without relying on walls. Warriors, carriers and lurkers are useless unless there's a push out of the FoB, Spitters don't do enough acid damage/high cooldowns, Burrowers are not a real threat... You get it. It's just boilers and trappers vs the world. Which, together with the req changes, obviously leads to engineer nerfs, because you HAVE to have those castes, they have to not be bald, and that's basically all the xenos can do against the ticking bomb of defcon. If you don't have them, you're screwed.
The solution, to me, is to deescalate. Having a few strong cades suck, cause the situation doesn't change, and it feels like a grind. Having cade lines fall and get rebuilt is much more engaging. Cades need to be plentiful and weaker. Ideally, spitters would be better at dealing with fobs by... idk, refreshing cooldown if they spit on cades (and providing engies with a nuanced access to water (maybe a water condensing machine that requires a resource). Ideally, boilers would not be able to carpet siege the fob (maybe with a machine that can be ordered by req/engie vendors, or salvaged around the map), and get a weaker railgun ability, so that they can still solve the frontline issues (which new boilers do pretty well), while not fucking over FOBs. Ideally, Teslas would be nerfed, to not inhibit the queen (that's what the flag should be for), or make it so that it costs a lot of resources. Ideally, the engineers would have a power grid of sorts, to limit the automated defenses in a flank (while not limiting the options).
When you have limited tools, you have limited things to do, and things get boring, but having too many tools can get out of control if it's not gated by a mechanic (like the power grid)
I do believe that the deescalation + power grid is a change we need. If it's well designed (which would take a while), it will give engies a problem to solve, it will force Bravo to allocate resources (which while not for everyone, bravos enjoy), and it will limit the sentry spam, to give the xenos a chance to attack. This will allow combat engies to be somewhat decent again, and have a small but reliable source of mats, while not being able to build real FOBs without power (unless you overcommit on the front). It will allow engies to do something fun while the ungas do their thing. It will allow xenos to have a more fun experience by capturing marines that don't manage to vacate a cade line, and see the battle line move, instead of butting their heads at the same cade over and over. It will make sure that if there's a tesla there isn't anything else to stop xeno pushes, and limit the silliness, and it'll make it so that cade lines fall and get taken again, which is the fun thing to experience.
Having stuff needing to get salvaged to bolster the FOB would give the bravo ungas that want to QRF another thing to do outside patrolling and protecting the engies, or will change charlie's orders from power and unga to power, salvage and reinforce. And could also make forgotten parts of the map more interactive or something, and stop the MetArUsH cries, Idk.
TL
R: Powercreep killed engies. Nerf teslas to patch it up for now, deescalate, and instate a power grid to manage the sentryspam, and make shit fun again. /rant