Dread Necro is a base class, so it can be taken from level 1. If all of the other players put their heads together and think, they can ALL take TTS and the Dread Necro can top EVERYONE up after combat.
But really, infinite or near infinite OOC healing is amazingly easy to obtain. The player is paying a feat and playing a specfic class to get this benefit. The player could just as easily be a Binder (Tome of Magic) and bind Buer to gain Fast Healing 1 all day, and the ability to heal other players for 1 HP/touch as a standard action or 1d8+level as a full round action 1/5 rounds. She also grants you and your allies within 30' full immunity to poisons, diseases, and the Track feat.
Or buy a Wand of Lesser Vigor (CDivine) which heals 550 HP for 750g over 550 rounds (out of combat, this is amazing, in combat, not so much). Alternatively, MIC has the Healing Belt, which heals 2d8 HP per charge @ 3 charges/day for 750g each. A half a dozen belts will heal 36d8 HP damage each day for the same cost as a CL3 Wand of Cure Moderate, but again, will take a handful of rounds, and thus isn't really that amazing in combat. A single SNA IV will get you a unicorn, which has a Cure Moderate + 3x Cure Light wounds, 5 levels of cure for the price of a 4th level spell (spontaneously). The Touch of Healing reserve feat in CChamp and the Draconic Vigor aura (available to Dragon Shamen, or any dragonblooded character with a feat to burn) provide infinite healing up to 1/2 HP.
There are plenty of consumable resources for you to tire your players out. Spells, for one, combat or utility. Also, charges/day from a lot of the stuff in the MIC run low with multiple combats. Really, if you step out of core (or even within core, with CLW sticks), there is almost no reason why a PC should ever start combat with less than full HP. As long as you understand this, and plan for it, its not THAT much harder to balance. A Dread Necro who burned all of his spells is reduced to meleeing or plinking away with his composite longbow if he picked his proficiency right. That alone is worth taking a break to rest and regroup.
Required reading for anyone who gets browbeaten into playing a "healbot" cleric.
EDIT: Holy necromancery Batman! This thread is almost 5 years old!