Now that I've posted I may as well chime in. Before I start I'd like to point out that these statements are coming from what things look like on the test server.
Alrighty, so here's the deal. Both a Cleric and a Disciple have the ability to deal with close range fighting, the Cleric with its natural tankiness and the Disciple with its disruption abilities and passive healing. Now, the real distinction comes in based on playstyle, like Kainzo said. If you want to focus on healing and not much fighting or otherwise, Cleric is just the thing for you. If you'd like to be in the thick of the fight with your allies, dishing out damage and heals and support, Disciple is what you want. A disciple can't heal themselves (or others) as much as clerics can, obviously, but the disciple fulfills different roles than the cleric. Lemme break it down for you.
The disicple is a healing, supportive bodyguard. You are adept at disorienting, dislocating and messing with people. Additionally, you have a pretty spammable instant group heal that heals allies for 110 hp, you for 84hp. Even more, your melee attacks heal yourself and your allies (provided that they're in range), and in times of emergency you can balance the % hp of your entire group (again, provided they're in range). The disciple is really effective if you're a good fighter and know how to manage your situational abilities, while utilizing the area around you for added effect. See a body of water? forcepush an assailant into it. That'll slow them down, while the rest of your team takes on what's left of the enemy group. Someone's beating on your caster? forcepush the guy way, or knock them all up with ironfist. Group got plagued? Chakra it away while healing for 110. Of course, it is lacking in pure heals and if you don't fight then you're going to have a harder time staying alive than the cleric, but you more than make up for it with your array or support/situational abilities.
So, TLDR; Disciple is more support oriented bodyguard-fighter with less healing but still able to hold it's own in various ways. Cleric is an almost pure healer, adept at healing their group for quite a bit with either aoe heals or large, single target heals. Survivability is also greater as a cleric, as you have other invulnerability/group invuln abilities that lend to that. Take yer pick.
