I don't even bother with buffs on Despot besides Utsu. Bio and poison kite til vert timer is up. When convert is ready toss a grav, nuke away my MP, and vert. Only buffs worth using are RR and utsu.
I won with 316 skill and 5/5 ice when I was first learning to solo in sky:
276 base
16 merits - 292
4 elite beret - 296
5 spider torque - 301
15 af body - 316
but my resist rate was pretty crappy and a lot of straight tanking was involved. I used zipacna and despot as my main gil source for a while, and my gear gradually got better while the mobs stayed the same so it was easy to see the difference.. resist rate was floored between 330-335. 'accurately' is a pretty vague description, I'd say you can win 99% of the time at 320 skill with other appropriate gear(what you listed is only 310.. you can get another easy 4 from elite beret and probably win a fair amount of the time with just that, but more merits would help a ton). You should spam gear swap macros while running if ice break lands on you, you'll move a tiny bit every time you swap and get out of his range eventually. I said 99% because a thunder break + a couple crits will kill you as a taru if your idle gear isn't too great.