Yes WHM is still fun but it depends what you mean about fun. The thing with WHM in a raid capacity you are always the primary Healer since you output a lot of HoT so your DPS up time is a lot less than a SCH or AST which put out more buffs and mitigation utility and SCH has a pet that heals so it depends if that is fun for you. In most content though your heals are so ridiculously strong that you can remain in cleric stance most of the time and just throw out some DoT's,and use holy and assize for group damage and stuns or just stone III on a boss and DoT's. You probably want to use holy less with a DRK though they like things to hit them so they recharge mana XD.

WHM the question to ask is "Do you want to be a Healer?" but with any class in the game it's about learning how to play it and learning content so then you can start thinking outside the box like "What can I do here to contribute to the fight" outside of just going through the motions.