As for the actual finale... Eh it was ok. The action looked cool, but Kuvira was just a weak villain. She's just a fairly skilled metal bender. Korra should have been able to take her out easily. Giant Robots are fun and all, but it just didn't seem too practical. Korra relating to Kuvira just seemed forced. Kuvira went so far beyond, "just trying to protect her people" that it was riduculous.
Ultimately, it just seemed like another season finale. It was OK but it wasn't like, the culmination of the whole series. It didn't feel any grander than the endings to season 1, 2, or 3.
What DID need resolving was Korra figuring out what it meant to be the Avatar, and I really didn't feel that. I guess you could say her job is now to make the world safe for democracy after sort of rejecting communism (Amon), theocracy (Unlaq), anarchy (Zahir), and military dictatorship (Kuvira), but they needed to expand on that.
I'm fine with Korra being with Asami, but the build wasn't there. They were obviously close, but nothing about their relationship seemed sexual. Yeah, she wrote to Asami and not the others, but that could just mean she's more comfortable talking with a girl her age rather than an ex or a goofball. Yeah, she blushed when Asami complimented her, but a lot of people get embarassed about compliments. The avatar world has a lot of close same gendered friendships (Mai and Ty Lee for instance) and none of them have been hinted to be sexual.
They really needed to do a better job establishing this relationship as something beyond friendship. A scene with Korra comforting Asami after her father's death? The two expressing more concern over each other's safety prior to the final battle? I dunno, something.
And Korrasami was frankly unnecessary. TLA ended with a kiss, but it made sense. The relationship between Aang and Katara was prevelant throughout the whole series. It was basically the reason why Aang was fighting rather than being the reluctant Avatar he was. The arc had to be resolved. Korra's lovelife was put on the backburner since the end of season 2 or so. There wasn't a big unresolved romance arc that really needed resolving.