Dunno why you say not very well, I can hold hate as well, if not better than a pld/nin. Only problem is, there can't be mobs in aoe range.
1583 base hp, with high breath mantle (also 8/8 hp merits), I'll get cerberus mantle at some point. With carb thats 1758 hp. +22 enmity
Spells I use to keep hate:
Actinict Burst - 180 CE, 1020 VE
Temporal Shift - 180 CE, 1020 VE
Jettatura - 180 CE, 1020 VE
Exuviation - 640 CE, 640 VE (diffusion exu. hitting whole pt generates more hate than invincible)
Blank Gaze - 320 CE, 320 VE
Magic Fruit - depends on how much you heal.
Saline coat (rarely) - 1 CE, 480 VE
I also put in magic defense bonus trait for ultima and such.
CE is permanent hate, VE is temporary. I use the first three to get quick hate, if someone lays a heavy nuke, or I just need more hate at that moment. Then once I've established hate, I use more of the exuviation and blank gaze, to build permanent hate.
With a rdm and brd, your mp never even goes under 300 (and I'm an elvaan). Very easy to hold hate.
As for cannonball, this is the build I use, don't really use the fire staff/grip unless I'm using azure lore, most the time its ifrit's/genbu. I've broken 2k easily on most gods, KB, etc.
Only trait my spell set gives is defense bonus, and I use taco's for fewd.
I had screenshots of over 2.6k cannonballs to byakko, but I can't find them ><
But to answer Ewok, damage wise, blu only really has potential on kited fights, using cannonball once a minute (one with SA, next with CASA). And we can tank very well, but limited to few fights due to our spells being AoE.