I'm 8/8 HP merits and don't have a ton of MP gear, more enmity geared so the only spells I will use are Sleep 1 / Stun / Bind
Those by themselves can hold enough hate solo tank, if you're trying to tank a mob like JoL where you will have 6-10 BLM nuking it to hell and are trying to hold hate even with another tank (PLD/NIN can generate alot more hate on this fight from -ga's >> cure themselves spam) then what I just do is conserve my JA's.
I try to keep it so a stun > sleep combo can take hate, but if say thundaga III just lands and PLD cure IV himself then Rampart I will definitely need to pop souleater and maybe last resort to keep hate from getting too one-sided.
If you have MP merits and some MP gear I'd try to stick to aiming to keep hate only with spells, it's safer than relying on JA timers, but sometimes is necessary no matter what setup
Also, I use San spells to help hate a small bit too, its not much but unresisted they pull some nice hate.