I find assault rifle with full auto to be best with bloodspiders, actually I find myself preferring assault rifle over plasma rifle because with assault rifle enemy is still killable with full auto mode from typical range where I spot enemy, while with plasma rifle soldiers are not hitting the target in any other mode than snap shot it seems, surely if enemy is around 3-4 squares away, then plasma rifle is better, but 10 squares or more is range where I mostly need to shoot at.
Of course I must note that I play at very easy and find that level to match my skills (that are none) perfectly, enough challenge to keep troops alive but not frustrating murdering challenge like most games I find. I play to enjoy not to work
Also I have found out that sometimes those lizzard guys retreat and run around a building in attempt to flank me or surprise from behind, also they seem to attempt to get better shot by going to building from backdoor and then approach without being detected to closer to my troops. Maybe I just imagine things, but if it is so, then I find AI being much better than I have seen anywhere else.
Sometimes they get however bit foolish, having 8 guns pointed at one AI he still runs to open in attempt to get those civilians, or maybe he just was getting mad rage as I had bombarded him with grenades of all sorts from cover.
I guess moving and trying to maintain being covered despite enemy movements and still have several guns pointed with reflection fire on would be way to go, my attempts at that have been somewhat successful, 3 guys shooting 3 round burst with assault rifles as reflection fire has had good effect to lessen deaths among my troops.
I recently acquired lasers and things got quite bit easier with those, because of range and sheer power, now only two guys need to shoot lizard and it goes down.
However I think that with more difficult setting it will become quickly frustrating at least for me, surely it is superior enemy that one has to fight and at normal level I would think that it should be quite a struggle to fight off that enemy, playing very hard level probably should be nearly impossible with only perfect tactics leading victory. I'm too scared to even try of such.
Oh yes, plasma grenades seem to work quite nicely, but one needs to have them stop right next to enemy's feet to them to be working well.
I keep medikits at holster, along with grenades that I have also at belt, spare clip at belt, haven't really used Secondary weapons as rifles work so well even from close range. I try to get them come close instead of me going close also, that way they I get less reaction fire damage.
Flamethrower is nice inside of buildings, but outside I really can't find much use for it because of limited range, but it has great amount of power and it is really good against bloodspiders if used in reaction fire mode, candle light to blood spider and then it is easy to kill with lesser firepower.
Inside houses, I use group of three usually, keeping those corners covered and remembering that I can usually get glimpse what is around corner and come back without enemy firing at me, then throw grenades by bouncing them off from wall to make them go around the corner, evens things a bit when reaction fire ensues as I wait behind a corner for enemy to run into gunfire.
Probably I make lot of errors, so I like to play my first campaign at very easy and I must say that I enjoy a lot of it.