I agree with most of this, except for the tankiness part (excluding crushers).
Nades in their current state are pretty shit other than for clearing resin structures (only eggs, sticky, and weeds pretty much). While I do not think marines should be able to chain stun, cause that is already AIDS enough from the xenos side, there should be a way to guarantee a stun that is a result of good marine play and xeno misplay. In its current state, explosive resistance just makes nade not scary while marines still get a shit ton of damage from nades. Xenos should not be able to get cheesed by a single marine spamming UGL with its short fuse, but xenos should also not be able to not pay attention, walk into an HEDP nade, and then act as if it was nothing.
In terms of fire, I just think there should be a debuff (other than speed) applied for being lit on fire. I like the pheromones disabler they have in TGMC, but ultimately it's up to devs to decide on a particular debuff. However, healing should 100% be disabled while on fire. Your priority should be to get the fuck out and put yourself out rather than having some wiggle room to do whatever the fuck you want before putting yourself out. If not handled ASAP, fire should kill you, as it does for marines.
Also, side note with barricades, FOB sieges are not fun for xeno. I don't know who would ever get the impression that wasting minutes upon end fighting lines of barricades with barely any end in sight, ESPECIALLY if you do not have crushers/boilers/queen, is fun, but it isn't. It is an annoying grind, especially with lines of plasteel cades that barbed with an active engineer and sentries/M56Ds. Big Red is probably the map with the worst examples of annoying, time-draining FOBs. Good engineers literally open up all the flanks and fortify them to shit, so wherever you go you're forced to spend minutes pushing, and god forbid the marines catch wind and decide to fortify the shit out of that position, especially with ASRS. It's a cycle of autism.
In lieu of autism FOBs and grindy sieges, I just think FOBs and sieges need to be reworked so xenos don't feel useless attacking an FOB without a boiler/crusher/queen, and marine FOBs aren't so weak that they are useless. I think marines should be able to come back if they hold their FOB well, but sieging good FOBs should not be an exercise in futility for xenos. How to make this happen is another story though.