I solo'ed this quest as a 97 Retribution Paladin. I would recommend you pull him away and into the shallow water so that nothing else aggro's during the fight.
Keeho has two abilities that cycle throughout the fight, one after the other:
1. Intimidating Roar, which is very similar to a Warrior's Intimidating Shout that AoE fears anyone in melee for 4 seconds. Has a cast time, can be Interrupted and should be.
2. Hack and Slash, which is a STATIONARY channeling attack he does to anyone in front of him. Can be avoided by side stepping as soon as he starts to cast it. This does the bulk of his damage and should ALWAYS be avoided. An alternative method if you're melee is to just keep doing circles around him, and therefore whenever he starts to cast you will already be to his side and avoid the attack.
He does not hit very hard, but he does have a lot of health. If you have any abilities that can heal while he's channeling his Hack and Slash, that will increase your chance of success. He hits plate for 4000 to 5000 each melee, and I have 142,000 health.
If you have cooldowns, try and save them before engaging.