Tank is neccesary IF you have mages..
And no, mages will not run out of MP, the low lvl bosses die fast and they have BTS lvl 6..
Have you guys even fought low lvl rbs? It's not so complicated as high lvls.. it's pretty easy and fun.. and kinda worth it on low lvl server. (like 3x)

pff talk whatever u want
mages are NOT effective-tryed it
if u add tank and mages u gotta add also recharger(s)
gg

i go for pt of orcs