Thanks for the input guys and I'll definitely check out the link that Myrrh provided. I've been using the Hunting Grounds guide from wiki which does have some inaccuracies. For example, Magic Fruit. It says that the spell can be soloed starting in the low 40's but you can't learn it until at least 53. How can you solo the spell in the low 40's if you can't even learn it until 53?
I guess my shitty luck in real life is spilling over into the game. Pinecone Bomb wasn't too much of a problem for me but looking for the treants in Jugner was. I got the spell after killing about 5-6 of them. The spells I've had the most trouble with so far are Geist Wall, Jet Stream, Blank Gaze, MP Drainkiss, Blood Saber, Sickle Slash and now Self-Destruct. I thought Wild Carrot was going to be the same way but thanks to the Goblin's Rarab in Bibiki Bay I was able to get it with minimal difficulties.
Pre 60 (or was it 50?) you can learn spells roughly 10-15 lvls before you can use, w/o af. I learned Exhuviation (lv75) at lvl 60 when it was released. Magic Fruit is 58 if I remember, so I think 45 or so would be a safe lvl, barring how well you can kill the opo's at that lvl.
Spells are fairly random from what I've seen. It took me 2 trips at ~6hours each to learn Spinal Cleave, which is a "break weapon" spell. Those btw, are the worst to learn. Random chance to break weapons, even if you are good at it, and then random chance to learn. As to Death Ray, I used to MB it at the end of my solo skillchains, think it did roughly 200 dmg on average, bring my solo SCs total dmg to like 400+ at the time.
It may sound twisted, but I enjoyed learning spells, at least when I was able to solo. It was cool to learn the behaviors of different mobs, not to mention seeing what you were capable of soloing on the job. You can sometimes effect what move the mob will use next, or at least the chance at it happening. Bulking up on defense seemed to get taurs to use Frightful Roar more, and using the spell in parties seemed to make the crawlers spam cocoon more. To keep bees from using final sting, you couldn't hit them fast, then give them tp, you had to feed them TP slowly from the start (barehanded, then turn your back and just let them hit you for a while when they got too low).
Maybe try dropping the bombs hp fast, while still allowing it enough hp to feed it TP? That may help to trigger Self-Destruct more. Also, mobs will burn TP more often while below I think 10% hp? Before that it's random, sometimes they will wait til they have 300TP to use.
If I didn't have to go through COP again, I would probably lvl BLU on another character, learning spells was some of the best times I had on the job.