New Tank item concept: Vangaurd's Cape

If you've seen Sancre's post on ironcald hydra you'll have seen this item in the comment section but i figured i'd go with his suggestion and make a original disussion on it, so heres the item https://boards.na.leagueoflegends.com/en/c/skin-champion-concepts/67VWFmv6-ironclad-hydra

Name: Vangaurd's Cape Build: + +500g total(2600g) Stats: 300hp 40armor 40magic resistance unique passive-Thorns: Upon being hit by a basic attack, the attacker takes 20+(5%armor)(5%magic resistance) as magic damage and applies grievious wounds unique passive- Vangaurd's Protection: whenever you take damage from an enemy champion you send out a pulse of energy that gives heals you and allies for 10-100+(10%-50%armor)(10%-50%magic resistance) over 10s, this can be proced every 5s and can only be proced once by a DOT ability. If an Ally who has Vangaurd's Protection already on them is hit by an additional pulse the left over heal is triggered automatically and Vangaurd's Protection is refreshed

i am open to all idea's and concepts on how to balance this item and look forward to answering any questions