Well as soon as I could buy AC, i went and bought another skill tree for just this reason. I went full tank build with war cry and everything and i have not looked back. My reason being, i have insanely high defense with a great amount of attack still. And this is how i did it.
First, keep your s-atk mag from when you were a damage hunter, the loss in atk you will see from going tank will be noticeable so having the extra 80-100 points you should have on the mag will help. (I have about 60 ability on mine as well) This helps counter balance the loss of attack from guard stance and keeps your damage up.
Next is to find a good sword and get it up to about 400+, last survivor is a great sword as it gives HP up and requires s-def to wield. This in my book was a great sword for a tank. Also you will want to pick up sword gear.
S-def up is a must, as without a def mag you will need them to use the higher 8* armors. I recommended the golden looking armors that look like they have feathers on them, as they grind out to a very high amount of s-def, plus put a nice rockbear soul on them and i think they max out at 200+ s-def per armor.
Also, the importance for war cry at max is almost certain if you are going to be full tank, if you just want to be a defensive fighter then its not as important. With war cry however they stick to you like glue and the other damaging members of your team can pummel them to death. Also at max it has a 30 second CD, with its active time being 30 seconds so they are always on you.
Of course you want just guard, because i've found out as a tank if you can throw yourself in front of an attack and just guard it, it will also stop the attack from hitting your teammates if they are in range. This is very helpful to being an effective tank, and something i use all the time on the new snow tiger when he does his leaping attack.
Here is my current skill tree:
I don't see the importance of getting the extra health, as the rockbear souls help out and you have to max the HP up's for them to be really useful. Plus I take at the most 60 damage from bosses attacks so I have plenty of HP to take damage with.
My current striking stats are 900 atk and 1000 def, without guard stance on or any med center drinks. So i feel pretty balanced.
Anyway this is all just my opinion and what has worked for me. Hope i have been able to help you figure out what you want to do!