While I can agree there is a lot of political infighting isn't this more a result of the iron law of oligarchy than anything designed on purpose?

Meh. I'm agnostic about whether it was "on purpose". Humans revolt and so select for governments that aren't revolting.

I'm not sure how the iron law of oligarchy results in political infighting, and i'm skeptical of the iron law of oligarchy, but I don't think that's particularly relevant if we agree about the facts on the ground.

Also generally I'm of the opinion that in the long run formalized check and balances don't really work.

Well, nothing works in the indefinite long run, unless your goal is entropy. It does seem to stop a lot of legislation from being passed / sticking in the US, which I suppose is only a benefit from a particular perspective.