Esker
Hero
In a 4 round fight that means you are killing 1 enemy per round. The first enemy gets his attack and you kill him that round. That means there's no incapacitated enemies left. So you attack one of the incapacitated enemies. You go through the rounds and kill him but in that time he likely gets an attack in on the party. So ultimately the party takes 4 attacks. Without hypnotic pattern the party would take 10ish attacks assuming focus fire. The difference is 6. Not a perfect comparison. But a starting point.
If your party does 1 enemy worth of damage per round then they probably only take one attack in that scenario, since they can all ready actions to hit each incapacitated enemy at one time, and then some of them get their actual turns on top of that, before the enemy can act.
It depends on the size of the enemy groups encountered. The smaller the group the less useful. hypnotic pattern is. The larger it is the more useful it is.
Of course. It's also not the warlock's only spell option. In a single-target situation, they might use Phantasmal Force, for example, or Banishment, which have a good chance of taking a monster out of a fight entirely until the rest of the enemies are dealt with (or in the case of Banishment, possibly forever).
Depends on the damage difference. But sure, it's likely not enough to keep up with a wizard or sorcerer or warlock in terms of control potential. Of course that's more about showing caster supremacy than it is showing the monk is bad. In fact, that a monk has much better control abilities than DPR classes at all may be enough to vastly elevate him over those DPR classes. Just as you argued with the warlock being much better than the monk because of better control abilities.
Yes, that's a fair point. Which is why what we really need is to put control and damage onto a common scale. I would suggest converting damage into control rather than the other way around. But either way.