ult summons 1 tentacle for every enemy champion hit, if you hit 5 you spawn 5 tentacles that deal full damage to anything you use your w on (which turns into a 2 second cooldown while her ult is active) this can result in 100-0ing a squishy in an r+w combo.
on the side of the e, it only does a % of the damage dealt to the spirit, base at i think 25%, so if they use all their damage on the spirit its like you have a 75% damage resistance for all of their high damage out put abilities. the e also cant kill you unless they hit you as well as the spirit, as it starts with your current health and as said above, doesnt take full damage. also doesnt appear to apply on hit effects to the effected champion. so things like twitch's poison, teemos, things that might kill you after the e expires, dont have any effect on the host body.
This is from what ive observed of the champion.
short form: ult has the potential to win a team fight, e cant even kill a single person.
hopefully this helps :P