I think the luck factor is pretty broken, it's kind of worrying that the response seems to be "eh, I don't think it matters too much, it should all balance out right"? Because that's not really how chance works. If you flip a coin 100 times that doesn't mean you are going to get 50 heads and 50 tails. Why does that seem to be the logic here?
It should just be more deterministic when you play a tier play up and when you get to play ahead your rank and when you play below. Like having ELO thresholds where after you pass it your next game is a tier above at a set elo range, so every team that reaches that level (or higher levels) has the same opportunities to test themselves at around the same level of competition.
You should also alternate between playing below and playing up, or something a little better than "it's random". If it wouldn't be a huge pain to see snapshots of teams ladder positions through the season (actually maybe Trojan's threads would be really good for this, I'll check this out) you could probably identify a huge luck advantage for same teams versus others (Hawaii Bulls being the obvious "we got screwed" team).