This is my Fire/Stone/Dark build. The PBAE in the dark epic works nicely with inferno. Aim -> Engulfing Darkness -> Inferno hurts.
And going Fireball -> Engulfing Darkness -> Fireball does good work when inferno is down. No travel power but it's auto-haste.
I almost forgot the other good reason for Dark, which is Darkest Night. Its a debuff toggle that gives 10 to 16.4 to hit debuff depending on spec
and -21% damage debuff. It makes you tankier than you ought to be:)
Sentinel - (Fire, Stone, Dark).mbd
Well I'm not a professional builder, but this mine. I test builds out on 4/8 Arachnos, Carnival and BP and it handles them solo.
I hear that's no big deal these days, but it's good enough for this mere mortal.
I hope it helps.
Sentinel - (Fire, Stone).mbd