I know for a fact that Well of Tenacity doesn't stack with Omni because whenever you go invis Omni simply overrides the Tenacity buff and removes it (I've tested this). However it's hard to tell if it works with PL, I'm leaving the video test I've done in here but I would love to hear official confirmation from a dev or mod. I'm 99% sure it doesn't stack but the dmg reduction is so low that it's hard to tell, also if it DID stack woulnd't it only be 5% because of how multiplicatively the buffs stack in Destiny?