It seems worth pointing out that "NS" for phases 3 and 4 are pretty different.
For Phase 3 you need to run zTalzin lead, zAV (unique), Zombie, Daka (zeta helpful but not 100% required), Initiate. Talzin/Initiate need to be at low-ish gear levels so they die off quickly. You want them dead, then they will constantly revive on basics, and the resists from the debuffs they try to apply will feed you tons of turn meter and AV's damage will skyrocket because of the repeated reviving-then-dying-again.
For Phase 4 it's zzAV lead, Talzin, Zombie, Daka, and Talia. No need to keep anyone at low gear levels. You're focusing on Nihilus only, and abusing AV's lead granting TM when your team members drop below 100%. You want to juggle heals so that somebody is at 100% TM as much as possible and Nihilus never gets a turn, while making sure to dispel Bonds stacks around 12-15 so that they don't outpace anybody's heals. Ideally you also want to get Plague on Sion & Nihilus at the start so they bounce it back and forth the whole time, which will add up to a pretty decent amount of damage over the course of a run.
My Talzin is too geared up to bother with the P3 team, but I run the P4 version regularly and I can usually knock off ~20% of Nihilus and about 13% of Sion (plague, Daka & Talzin secondary hits, and AV's AOE) with just "pretty good" mods.