yeah, that's why so many people are clearing them left and right. in pugs.
and actually he's very much correct. if you were maintaining 8 stacks of hots on everyone, not only you'd have to have perfect latency, but you wouldn't be doing anything else. theoretically - the probe is supposed to last 18 seconds. practically, you have to refresh it no later than 16 or risk both stacks falling off. moreover - without perfect latency, and inhuman reflexes, you won't be refreshing it every 1.5 seconds on a dot. it will be closer to 2 seconds per probe. which means that this is literally all your are doing. no cleanses, no other abilities used, just going through probe refreshing rotation. and that's not counting mechanics that may add time to that already tight interval
Just to clarify, once the encounter starts, I move on to healing whoever needs the heals and let the HoTs run their course until I get a good chance to refresh them. When the fight is over, I slap them on again to save time as everyone can heal on the run. Maintaining the HoTs with four players is easy, but with eight there is very little time for anything else and therefore it won't be a good strategy.