Advice on formation, please.

[Kibo]

Hi guys,
I am a GunM lvl 61 and my current formation is:
:vik::swm::swm:
:spm::malehero::bst:
:arc::mnk::sha:
I am doing almost only PvE at the moment and I am not considering mercs over lvl>90, I dont think I will ever get there.
I am thinking of changing monk for witch and archer for artillery.
What do you think ?
Thanks for any advice,

[Thlurp]

if you only pve, ditch archer for proph and 1 swordsman for arti
put bt to front in place of the sword

theres not much more we can do without higher mercs so just keep lvling ;)

and trust me, 95 is pretty easy to reach so i would consider mercs in that range