nct should be good for solo like ^ said, especially with PK. exp per kill should be around 100-200k from my experience (vip+bmx3+spotlight/exp mod) and the BB gives around 18m?? exp per big bell turn in.
for bio4, you can get into parties since usually its not even because the exp mainly comes from BB, so vip is almost a must to get the 160m?? full exp per turn in
bio4, my suggestion is soul cannon balls for celia and iron for others, but this is if you can tank celia's skills (fireball, thunderstorm, frost diver, cold/fire bolt, heavens drive, earth spike) some of those will be blocked by magnetic earth. so you need a good elemental reduction. i wear a wind unfro and leib olmai top and mid, i switched from v shield to mad bunny for dmg, but the v shield should help you tank. i deal around 40-100k per CC on celia depending on buffs thats why i attack her. dont do it if you cant take the exp loss.
focus on randel bombing. +9 kvm mace should let you deal close to 300k per bomb, or any weap you can find i guess(i used an ea enchanted erde w/ 2as before the kvm and it deals around 150m per bomb). and then just bomb everything aside from celia if you want. just always target randel first. turning on effects can save you bombs if you can handle the lag since pneuma is there. i see a lot of people waste supplies and sp from targetting chen in pneuma.
and your homun might be a nuisance or tank depending on your view. the thing is, after every g wing, the homun will always be attacked by mobs. PK wont help the party much since the dmg there is ridiculous. since you always have to resurrect it, you might be the other first target per g wing since you might be casting once you fly, and then you will die fast.
btw, i use pyroclastic so my dmg might be based off of that, so your dmg will be different based on those. test it out first on a party and see what you want. i tried nct myself but i cant take the dmg even if kiting them so i stayed in bio4. but you have PK so you might be better in nct than bio4. try out each area and then go to the better one.