How Should I Kill Bob's Reincarnation?

Don't try and solo him if your build is heavily based around elemental damage
I'm Level 100 and still can't solo Bob because of this

 

He has High elemental defense....

 

Agreed.
I was totally clueless about his defenses the time I fought him since I was in a group and his health bar replaced his elemental affinity/information the moment I came in... Ended up using an Empire Builder with all 8 slots filled with T4/T5 powders across all elements XD
Somehow managed to get my share of the drops though..

To the OP, try gathering a team to assist with the battle, but with the recent boss drop nerf you'd probably still have to find a decent weapon

 

you build a wall infront of it and make it pay for it, so bob's reincarnation get's poor. then you strike at night. ez.

 

Get a mage partner/potions also have high mana regen and spam arrow shield he won't be able to touch you then just shoot him down as for a bow either get one with every high concentrated damage in one element or mostly neutral.

 

Unlike Qira, Bob's elemental defenses are not that hard to penetrate as a level 100 class, so you should not have too much trouble even if your build is based around elemental damage.

Unless by 'elemental damage' you mean like 500 damage in each element.

 

Whimsy with three Tier V Air Powders.