Don't fear the warden's Font of Life; embrace it. As often as you feel appropriate, throw monsters that drop lots of status effects* and ongoing damage on the warden, e.g. beholders, carrion crawlers. He'll be challenged and the group will be happy to have him in the party.
As an example, my group's warden had much fun with a gauth beholder in a boss fight. I targeted the warden with the brunt of the gauth's attacks - 2 eye rays each round so he could make good use of his Font of Life. Thanks to him the group survived the encounter, and they were all bloodied and out of heals (with the cleric having gone down twice during the fight).
* I'd use stun and dominate sparingly, though. They're quite annoying.