I've seen lots of DRGs sure... but if I remember correctly most of them are DRG/WHM.
Why not THF as a sub instead of WHM? Well because a DRG/WHM is a kick-ass solo artist. Why sub THF for gilfinder, when the downtime from resting every so often may very well mean less gil than a DRG/THF.
Or maybe go DRG/BLM so you can use -ga spells to take on multiple mobs at once.
Whatever though - it could also be that, like you said, they just have no idea what they are doing.
Keeblerelf; Kingdom of Bastok; Rank 10
[75 WAR] [75 PLD] [RDM 75] [RNG 65] [NIN 61]