Druides are just as usefull as priests - it all depends on what your preferences are in RoM.
- do you want to do just pve or also pvp?
- do you prefer a heal that can provide good buffs for their party?
- do you care to cleanse a max. of debuffs by yourself?
- which heals are already in a guild & which would provide advantage to your raid-buildups?
pve: all priests and druids could heal everything well geared and well buffed
(some combos provide a lot of elite-skills to make your job easier, some dont... if not playing "all-heals-elite"-combos one is better of to "at least" provide nice buffs for your raids dps [certain buffs might seem nice but not all can be stacked on other nice buffs and just replace them -> d/wd is loved by mages since the mdmg-buff stacks with the m/p+p/s-matt-buffs / d/w used to be loved by dps, after all it cant be stacked with priest-patt-buffs since some chapters and got quite useless, p/r + d/r can provide nice buffs for p-dps+m-dps] - just check whats most needed in your guild or/and what u like)
pvp:
p/k is op when it comes to rush with a party - nice pdef + selfheals
d/wd got nice pdef, using elite60 it also got "sort of selfheals", the nicest advantage of d/wd is the use of briars on castlegates or being used as portable aoe-heals for dps. no combo can healup gates as well as a good d/wd after all.
others already talked about different pros&cons - siege war made me swap from d/s to d/wd and by now i really love being d/wd as well in pve