Some comments for the 3rd fight:
 
Tank: Just Needs one impair for Psychic renewal. Everyone in the Group must learn to evade the AoEs from the Huggies. Most forms of mitigation will not work against the Spider (e.g. all percentage based reduction like Signets, wards, flak jacket, fleeting fortress). The only form of mitigation seems to be defensive procs (block, glance, evade). For this reason i would suggest hammer chaos. Stoicism can still help for getting agro quickly, which is kinda important because of healing agro. Whippersnapper will not work as an impair, just use Crack for the debuff. It is also possible to go buff tank (for short fuse), but you then will require slightly more healing.
 
Healer: go fistol, backup drone is almost a must have. Also take 6-7k health, as you will have to tank some shades, beasts, and huggies.
 
DPS: Best single target you have, with 2 actives for AoE - eg.g pis/shg with scattershot and bombardment or melee with aoe builder and ctp. The strongest dps i have seen were melle, hammer/blade in particular. However pistol shotgun also put up some nice numbers, and you Need the buffs. Percentage builds and proc builds both work.
 
I would suggest to use the buffs with the cooldown passives, but there are also tactics without the passives. Buff at the first beats. Kill the beasts first, then the 1st Huggy. If the 1st Huggy isn't dead before you move to the Spider your Group will not have sufficient dps. Actually, the 2nd Huggy should at least be in it's 2nd shield when you move. Psychic renewal from the 2nd Huggy can also be impaired, but it is tricky. In total, you Need about 5k group dps to beat the fights. The fight can last 4:30, maybe 4:40 max. The dps will pick up slightly on the Spider over the many shield Switches with the shades, beasts and huggys, but you probably need to parse 3.5k - 4k in the initial phase. Everyone should have a leech pot available to extend the allowed time by that potions duration when everyone has filth stacks in the end..