Give your reasoning please or don't post useless information.
Ok I will spell it out for you. This information is not useless, and I did not not expect to have to explain it in such detail.
1. Slow: Clerics have always been heavily armored, at least the Cleric through HC lens. As a result, their strategy is pretty much the only healer strategy that does not require about 75% kiting (replace "kiting" with "position control" for disciple). They can take a hit. The class is balanced around being hit more than other healers. You say your heals are canceled by most spells? No idea what that means, there are 3 silences and several CC moves in the game... Anyways.
Cleric's survivability is through its solid single target heals, group damage mitigation skills, and solid armor, NOT through mobility. You need to realize you are suggesting a new direction for the class, which I doubt you realize fully yet.
2. AoE damage skill - There are two things I would like to mention. First, I said I do not see them needing one in current implementation, because clerics perform competitively at both lower level pvp (they are easy for new players to not lose with) and higher level pvp (they are, in my and others opinions, the highest win %, and most difficult-to-combat healer among the best pvp match ups in the server). Therefore, if such an AoE damage spell was implemented, some other aspect of the class would have to be changed, or the AoE would have to have a large mana cost to the point that the Cleric has to choose between dealing mediocre damage and mediocre heals, or light damage and stronger heals.
Second, I believe that the AoE damage direction is the wrong way to go for Cleric, because Cleric plays an important role in being THE healing class. Clerics deal less damage than other healers for a reason, there is an appeal to some players to a more heal-centric healer. If we were to change Cleric to deal more damage, it would be less unique of a class, as well as requiring the re-balancing of other classic Cleric attributes have been declared "here to stay" by Kainzo.
My suggestion would be to suggest what overall NEW direction you are interested in seeing Cleric take, and see how Kainzo/staff/community respond. What will NOT be met with success is suggesting multiple major alterations to a competitive spec without also mentioning what the trade-off will be (what would cleric lose for increased speed or an AoE damage? less heals? smite does 85 damage? more difficult mana management?).
TL: DR Clerics are slow in lore and have no AoE damage skill currently. Since general consensus and community pvp experiments have shown Cleric to be a strongly competitive class choice, if we were to make them faster or provide them with more damaging skills, changing of other classic Cleric attributes (strong single target heals, strong mitigation) would likely be required.
edit: I suspect Cleric tweaking is nearing perfection for current balance, but we will see what all these new ideas bring to the spec.