WHM melee could be decent, but not worth it in the long run. WHM club skill is B+, which is pretty high for a melee skill; however, that still translates to 3+ skill lower than what most melee should be using with few exceptions. To top it off, the gear we use should be focusing primarily on MND and MP to get the most out of our cures.
Yes, clubs do suck. The clubs mages should be using have MND, INT, MP and/or hMP All of those clubs are very low damage and have terrible DPS. If you do chose to full time a maul type club which have much higher base damages, they still have comparatively low DPS. Even at low levels where meleeing might even be considered, WHM weapon skills are plain terrible and actually remain terrible all the way to Hexa Strike. Having a PL does make it possible, but once again, like Courtney said, feeding it TP can have much larger impacts than just nasty AoE. More specifically, the instance of fighting crabs and the use of Stoneskin can extend fights drastically. That being said, I don't think there is a mob in the game that one can honestly say feeding TP isn't going to impact experience outside of maybe a manaburn.