I don't see any of the 3 being an "AOE" healer. With proper CC except on flashpoint bosses there is very little splash/group damage. Sage's AoE is level 31 talent that you can't get until 40 at the earliest. I don't know what endgame is going to look like, but a heal that costs 100 force is not going to be spammable. It will be an Oh Poop! button and will drain you of your ability to heal anything else if used very often.
I also don't buy the scoundrel is better in longer fights scenario. If you spec properly, Sages are pretty efficient. I can stay pretty much full unless the whole group is taking damage and I have to spam heals constantly.
This game is going to require coordination, CC, communication and otherwise not sucking for 4 man groups to pull off the more difficult content. No healer can keep up with a bad tank or dps breaking CC.
Shizuru
31 Jedi Consular Sage
Tarro Blood