Yes a Cleric would make life easier, but life doesn't need to be easy. A Paladin and a Tactical Warlord who both pick some extra healing abilities could easily suffice. If not, the Warlock and the Fighter can do some of their own temporary hit point buffs, and that should help out. When needed, the DM can decide how frequently potions need to be handed out.I didn't look at your party composition too closely. While the Paladin might be able to do a little healing, you're stuck carrying most of it for a large party, and Inspiring Warlords simply make better healers. Tiefling for the CHA bonus would be an option, since CHA boosts many Warlord healing exploits. But, really, an Inspiring Warlord (or even Cleric) might be better for a party of that size and composition.