Ironclad Hydra
While 
seems suited for Fighters and 
for Juggernauts, I think that a tank hydra would be a nice addition to the hydra's many heads
The Ironclad Hydra (as Dreadnought is already taken by Urgot) is suited for tanks to become tankier and help other frontliners that fight alongside them instead of doing more damage, and it rewards being focused on.
Stats (Can be upped or downed depending on feedback) 300 Health 80 Armor 80 Magic Res
Passive/Active (Values can also be changed based on feedback)
Cleave (Unique): Every time the wielder of the Hydra suffers damage it releases a healing pulse in a small area that heals ally units for a 10% of the wielder's current hp (The healing can be quite good, but depends on the rest of the team helping it too). The pulse is short enough in reach so adcs and mages wont get it if they aren't quite out of position and prone to being destroyed, but other frontliners are in a perfect position to benefit from it.
Crescent (Unique): upon activation, the wielder gets 15% damage reduction for up to 1.5 seconds, adding 1 second more for every ally unit hit by the pulse when cast. Ally units affected by it will get 30% of the wielder's total armor and magic res for as long as the damage reduction on the wielder lasts (20 seconds cooldown)
I would like some feedback to get this item balanced, and hopefully seeing it added later on, as a helpfull item both for tanks and tanky supports
+
+
+580g (total 3300g)
stats: 25ad
40armor
40magic resistance
100% base health regen
, to justify health, armor and magic res, having something like this in the end
to add some health regen, or even 
to add another interesting passive, although this last one could be a bit too overloaded in this item)
) or at least a shield based on something like 20% of armor+magic res of the wielder and 10% (so a full tank team can't abuse it that much) of the armors and magic res of the teammates healed by the active ( right now its a bit hard to get 300 armor and res on the same champion without it being helped by passives and that most teammates don't build armor or magic res apart from the tank, the shield would be a bit of a pity until very late game, but it could help to survive a little longer, similar to 
but for tanks)
). also cleave is something that is used to help with wave clear as a small amount of aoe damage and trying to change the fact that it does damage defeats its perpose. now if you want health applied then instead why not go with 
+
+500g (total of 2600g)
stats:
300hp
40mr
40armor
unique passive:thorns: upon being hit by an auto attack, deal 20 +(5%armor)(5%magic resistance) and apply grievious wounds.
Unique passive: Vangaurds protection: upon taking damge release a pulse that gives you and nearby allies 200% base health regen for 5s. this has a 3s cooldown. if a pulse hits someone who is already under the affects of Vangaurds protection the duration is reset and the health regen is increased to 250% this can stack up to 5 times for a total of 400% after 15s if 5 pulses consecutively hit a allied champion
passives are what you are discribing yet people still hit them simply because they are there and thats whose available to hit. If you could pick every team fight who you wanted to hit every one would just hit the carry and thats why tanks exsist is to get in the way of that, so giving this item to champs like 
there still going to get hit but now the enemy is punished and allies are rewarded for following up on your engages hence the vangaurd name. Also tanks fall into two categories Vangaurds, who initiate and do cc inorder to disrupt the teams and wardens, who defend and react to the enemies onslaught. in both of these cases the champion would get hit doing there job whether or not the enemy wants to hit them
or 
that not only is decimating your team, but also healing itself, healing his teammates with flat values everytime you hit it and even then is appliying grievous wounds everywhere)