[the broken]

Don't forget that the Errant was helping Iron Bars in the fight against the 5 gods. He can't help directly, but he can 'nudge' attacks away, and probably throw in the occasional energy burst. Possibly Bugg lent a hand as well.

Iron Bars doesn't know who the Seguleh are, so he wasn't prepared for such a difficult fight. He didn't know they were anything more than ordinary pirates. Also, the Seguleh fighting style involves precise targeting. In an ordinary fight, an enemy soldier stabs or tries to cut, and Avowed's man advantage is the ability to TAKE wounds and continue fighting. The Seguleh fighting style is all about targeting pressure points...
faster than most ordinary people can even move. If that femoral artery strike lands, Iron Bars is either dead or can't use his leg, Avowed or not. When he wasn't expecting any more than ordinary pirates, he takes time to adjust to the style.

And regarding the conflicting power levels, that makes perfect sense to me. Characters who have seen Iron Bars in action think he's one of the most dangerous people in the world. Characters who've seen Tayschrenn in battle think "How could anyone stand against him?' The same goes for Cowl v Dancer/Topper/Laseen. Reputations have been inflated over time.
Cowl played with Korlat...he may not be as powerful, but he's stealthy enough to knock her out, when she doesn't know the Crimson Guard are around. Anomander hunted him, and he lived. For watchers, that may be seen as "Wow, he has the power to challenge Rake" but that's not necessarily true. We hear that Skinner has fought Dassem to a standstill, but we haven't seen that fight, so we don't know if there were advantages at the time.