Thinking about her ult there are certain gods you won't want to transform into. Herc for example need defense and hp regen, things you won't build on a mid or jungle mage.
Merc needs crit, you can't build that on a mage.
You'd mainly use her ult to get access to other ults. That makes it super situational though. Ults like NU Wa's, useful but are you going to use you your ult with, I assume, a long cd just to kill one person?
Ares is a god most people are probably thing about but to use his ult effectively you'd have to use your 3 to stealth your way into the middle of the enemy then ult and then ares ult. That's your escape down and you won't have the protections to just walk out of there. Also you might not even survive the Ares ult without protections if the team is coordinated.
A lot of people are going to be wasting that ult as they learn her I feel.