Depends what you are looking for, endgame, just siege, or just fun.
But many classes are viable in endgame parties now
Tanks: k/w, k/p, ch/p, wd/s, wd/w
Heals: d/w, d/wd, p/r (sometimes p/s)
DPS: r/m, ch/r, ch/m, m/w, w/m, wd/w, w/s, w/wd, s/r, s/wd, s/w, (with magic party m/wd, k/m, d/r)
Support: (not much - no gear needed) m/wl, wl/m, ch/p, k/p, wd/s, wd/m, ch/m
Some of the DPS classes also double as supports, and as you see some supports can double as tanks.
For endgame you want to be one of these classes at least, siege is different in that more attacking and tank classes are viable however healers only really get 2 options, p/k or d/wd. (p/r can be good also, even though squishy it has its purpose.)