Dies to Removal

He can at least buy you tempo with it if you drop it on a late turn and tap a thing or two.

I must be playing a different game than you. I don't mean that sardonically or derisively, but in the environment I play in games are so often decided by "who's got the fatties" that I am trying to find ways to jam some "utility fatties" into my nekusar deck (even though currently the deck is mostly removal). And there have been several games where Mr. Pervert Demon has scared off a fair amount of damage or done a respectable amount.

So has rimescale dragon. Who also does a better than expected job of tying things down. Not saying he's great, but he does really well for a junk rare from coldsnap. And the snow requirements are light enough that you can just run snow basics instead of regular and be covered (I was running 12 basics before, when rimescale went in I just replaced with snow and it's never been an issue). Not a staple, but he's interesting to say
the least, and not hard to squeeze into decks.

How many times to you see font of mythos swing for 6?

Have you played with seizan in a multiplayer commander game? Outside of Nekusar he's a 6/5 for 5, with a group hug effect as big as his massive grin, and in games where politics matter he's your best diplomat. In a nekusar deck he goes from friendly to frightening add two more draws to whatever punishment you've set up, and an additional 2 lifeloss per turn. Trust me he hurts so good.

wild ricochet is a card I see in almost every deck with more than a token commitment to red, I'm not running it in Nekusar or Sek'kuar, but I was, and everyone I play with seems to agree.

seizan perverter of truth is another card I see a fair bit. It's not common enough to really be a staple, but when I ask people about it, it seems like they are only not running him because they don't know he exists.

Rakdos charm does all the things. Everyone in those colors SHOULD be playing it, whether they are or aren't is a different question. It's an instant, it breaks artifacts, it clears graveyards, and it makes the guy playing the token deck really sad.

Astral cornucopia will probably get there. It's a sizable mana rock that can make any color. I just replaced a darksteel ingot with it,
and I have been very happy with the result (except for when it got vandalblasted thanks to the indiscriminacy of overload).