1) It's not an adequate replacement for a cleric. Unless you play an inspiring build, you have no initial ability to bring healing beyond that of the heal skill itself, and even the inspiring build has a very limited healing utility. And there hasn't been alot of sign that raise dead and similar miraculous cleric abilities are on the table for Warlords.
2) It doesn't matter so much, because the combination of healing surge mechanics, rest mechanics, and no long term conditions elimenate much of the need for clerical healing anway.
3) It certainly easier to get by without a cleric. But based on some of the play test comments and what we've seen so far, it still seems to me that the optimal party contains a cleric and probably support from a secondary healer like a Paladin or Warlord. In fact, I'm wondering whether or not a 5 person party would benefit most from having two leader roles, plus say one defender, one controller, and one striker. And you could probably replace the striker with a second controller or defender alot more easily than you could get by without having a leader.