A few things:
If there is any amount of time a caster can sit, in combat, and maybe hope to get some decent mana from meditate, you will not truly be solving the problem of "sit, cast, sit". And the changes now have completely discouraged sitting. Now, people only sit out of habit, or if they are in their spell book, or if they are trying to stay out of the way.
Expanding on an idea that someone else had: What if Clerics had a line of summoned hammers (either an additional line, or change their current line) that, instead of proccing DD, procced some sort of group heal? Then, we've not only discouraged sitting by removing it as a way to get mana (which they need for heals), we've also encouraged doing something more interesting (meleeing) to indirectly accomplish the thing that they were sitting down for in the first place.
Carrying that idea even further, what if each casting class was given some spell or spells that allowed them, while meleeing, to *proc* an effect in line with their "traditional" role in a group? Enchanters would proc something that maybe AE mezzed (of COURSE with some sort of hate reduction or mem wipe component, or else it would be silly. And no, that doesnt mean they walk up to the ADD and start beating on it, waiting for a proc - They would assist the MA, and the AE proc would be do the trick. Additionally, since the mezzing of adds has to occur ASAP, maybe the Enchanters could have their version of the spell be a self-only buff that automatically fires on the first swing, or first hit.) Druids & Shamans could get some sort of self-only combat proc buff triggers a HoT. Necros could get something that procs a DoT or a small group lifetap. Wizards and Mages could get something that procced DD. This way, the people that are complaining that chain-pulling hampers their ability to do X when grouped, would have a way to accomplish X by walking over and beating on the mobs.
Last - If Clerics stay the way they are now, I would be excited about making a soloing BattleCleric!! I'll get to wear plate armor, I'll be able to heal myself, I'll have enhanced melee capabilities, I'll be able to lull, root, stun, nuke, I'll have a summoned proccing hammer, and mana regen between pulls will be almost instantaneous. And if I really screw up, and can't get my Gate off... I can just waltz right back, and rezz myself. : ) Certainly not boring!