RDM/NIN can tank HNM's really well on this server but it demands a lot of gear to do it. PLD/NIN is basically what most LS's use to tank stuff. Nin/DRK is another choice, not as popular on this server as it was during 75 cap retail, still works well though.

BLM is run of the mill endgame DD, most people have BLM leveled at this point.
Support RDM, much needed.
SMN is good on various fights, has lunar cry once you get Fenrir.
BRD and COR, very strong support. BRD's putting elegy on things makes fights way more easier to manage. COR's buffing BLMS and SMNS make things much smoother. Both are excellent for buffing melee DD's in the more melee friendly content.
WHM is very good on fights like Tiamat/Jorm to buff fire/ice ele resist due to gears that enhance Bar spells.

AND Bst is good for....... ??

It's own devices. But seriously, I've seen a BST75 with merits in Beast Affinity kill things it probably shouldn't be able to.

If I'm 5/5 in Beast Affinity, would that increase my Pet level for BCNMs and OWNMs? Example BCNM 60, would that allow me to have a higher than 60 pet?

prolly not....Below is what i see from ffwiki

Job-Specific Merit Point Categories
Upgrades in the following merit point categories are in effect only when the specified job is the character's main job and when it is level 75 or higher. All merits in these categories become completely inactive if the character delevels to 74, or receives a level restriction under level 75 under any circumstances.

I asked this in another thread but since this one brought up Bst and BCNM...I think it will be better served here now. I used to duo Wings of Fury and Royal Jelly back in retail on my BST. However, I heard a rumor that bst cannot charm in BCNMs on this server. Is this true?