Masrul, i will post a msg to u again once i reach lvl 30, currently working very hard to get my burst crack up.
Now let me share my experiences about Battle Assist, it may not be fully accurate as i am only lvl 29 now, but anyhow........
First off, you will have to decide whether to be a fast hitting 1 on 1 fighter, or an aoe fighter (gang bang

)
I am the gang bang type, so here is my suggestions, try to add your stats based on this ratio 4:1, sta:str. Why this ratio? I have tried increasing str to increase my burst crack damage, and each +1 str only give extra 5 damage. However by increasing sta, your fp increases, thus allowing you to do an additional crack burst which deal another 400 plus damage (higher as CB lvl is higher). This is a lot more damage compared to the measly 5 damage of the str. If additional damage is still needed, get a weapon with pluses, it adds extra 10 A.rt for each plus, that is equivalent to 2 str.
I have read many forums and they do not encourage adding so much sta because it does not adds knuckle damage, but indirectly it does, and a whole lot i might add, i am not saying those are wrong, but i felt they really haven tried out being a battle assist before they make those comments. So why do we still need to increase str, because u dun have an aoe skill until lvl 28, so u will be soloing most of the time before that, and extra str does helps a lot.
For buffs, only skill useful is heap up, quick step and of course crack burst for this kind of assist. U will need to walk fast to gether your mob, and any extra sta is always goods, additional def.
Well, hopes this helps. Btw, dex is not needed as skills will never miss. And now i am really having a whole lot of fun gang banging those giggleboxes.