I don't know what fights and enemies you are refering too. Sleep is difficult to use in late game, I would say it's useless. Hold Person targets humanoids which a) are so unimportant that the use of a lvl 2 spell slot for a control spell is a waste, b) are so buffed up that you have very low hit chances. Hold Monster is a lvl 5 spell with the interesting feature that it does not work against undead. It usually has also low hit chances against those which deserved it the most. You can build especially to make control spells work, but I did not find the effort worth it.
All mentioned crit situations demand some preparation. Which is often better used for other tasks. I like to have (currently) 25% crit chance in normal gameplay. As Warlock/Sorcerer/Fighter I can cast 4 EB in the first turn with some effort, some crit for sure and with some help from items it is good reliable damage.
BTW I also could use preparations with my build for fixed crits, but it is not meant for it. There is also the Illithid crit ability and a ring which grants you a crit to spare, you could mention. I have to admit that my build is not the craziest crit centered build (which might be Storm Sorcerer 10/ Thunder Cleric 2, but don't try it on Ansur), it's a more "normal" crit build. Huge crits worth some labour also demand a special ability which I don't have in my build.
