I have asked for permission from Alphamon Ouryukeb to do this and he said okay.

I don't want this to evolve in ranting and arguing like it could do in the accusation fix forum so please be civil.
If it's does I take responsibility:

How does the redemption and backstory of Tempest compare to Starlight or even Sunset in the first EG? Was it better handled?

Well Starlight's backstory adds more questions then it answers as unlike Rumble in Marks and Recreation, Starlight was proficient at magic and for what Starlight knew at the time so was Sunburst. We don't know why Starlight ran her commune the way she did and why she had planned to abandon the commune (the escape tunnel) given her backstory. Sunset's backstory is more strait forward as is Tempest yet Tempest's relationship to the Storm King does raises questions.

Tempest comes off as not trusting anyone because of the Ursa and her friends abandoning her afterwords yet she to an extent trusts the Storm King as she hands him power that she could have easily take for herself. It gets more questionable when the Storm King doesn't do anything to garner loyalty, even Tirek pretended to by friendly to Discord till he wanted to absorb his magic.

6151927
Well temPest may have felt she had no choice but to trust the Storm King as it was her only shot at having her horn fixed