I have played monored quite a lot last 15 months (but not too much lately, the field seems not optimal to it). I have thought of koth, but couldn't find a reason to play it.
-First ability is only relevant against Jace imho, as a haste creature, and not bounceable. In a "control" build, you are not really aggressive, and those 4 damage are cute, but not a great solution for 2RR.
-Second ability it's bad in most builds. If you already have 2RR, you should be able to play lots of spells. Maybe in a high costs deck focused on welders it could be a boon, helping play Wurmcoils or hellkites (for example). But too narrow imho.
-Ultimatum is great, but slow. You can't afford a card that costs 2RR and does nothing to hose opponent for several turns.
I could be wrong, but for 4cc i prefer Lodestone golem (easier to cast, hits harder, hoses opponents), rakdos dragon (a very dangerous finisher), lord of shatterskull pass (quickly gets out of bolts, dismembers, tarmos). Nevertheless I'd like to read your reasons to play koth
BTW there is a post for TMWA, you can check it for some similar discussions in monored.
