Make your healer stand right next to your tank (within melee range). AoE damage is the key. It should be a short encounter with this strategy.

Strategy

The Prince Keleseth boss fight begins when
you kill the last pack in the room with him. After pulling and killing
the last pack, the prince will come straight for your party without a
chance to rest.

It is important to mind the random Ice Tomb
applied to players, these can be burnt down and should be if your party
is low on healing. An ice tomb does approximately 8000 damage which
leaves most level 70s either dead or very close to it.


In addition to ice tombs, the prince will summon 5 skeletons which can
be crowd controlled, make sure they are grouped up when they die
because they will be resurrected periodically throughout the fight and
its easier to control them if theyre in a group.


Note: If possible its advisable to pull Prince Keleseth off the table
in the center of the room as the chairs cause line of sight issues as
well as it disrupts pathing with skeletons.
With your healer next to your tank, all aggro from the adds should lock onto your healer and your tank will be able to pick them up easily while the dps AoE's over the tanks head. You can also just have your dps focus fire the boss while the tank holds the adds, but killing the adds with aoe gives your healer a break between add respawns incase he's having trouble keeping people up.

This strat is ezmode for pally tanks due to consecration, but I'm sure a decent warrior can hold all of the adds with a little effort.