I almost feel bad, because he's using the fact that you agree with my Style, to make you out to disagreeing with him in full.
I literally have no idea why your being grouped up with me like this, but it's just a sign of the immaturity, coupled up with the close minded and inexperienced misconceptions that are flying around this forum.
It can NOT easily make or break any fight!
You can always point out a little thing here and there that will make or break any fight at any point in time. I can use your example totally against you, and bring up my T6 last week where my group killed the boss with only our warrior alive. Had I stopped for even 1 single GCD to cast stone skin on someone, we would have failed the fight. End of Story. I can then perpetuate that as being the golden standard from here to the end of tanking, and say that DPS from the entire party will always be more important than anything else, but in fact it's not the case.
You just want so badly to not be wrong, or called out, that your closing off any other points of view. It's a huge sign of immaturity, and quite honestly,t he way you respond to people with even slightly differing view points is disgusting.
It gets worse with your lack of admitting that your own example is so situation based per fight, that it in itself is a blanket statement.
I can turn by turn show examples of when it is and is not a good idea to cast Stone Skin. But generally, as a MT, you should not be looking at your party's HP, you should be avoiding all MASSIVE damage AOE attacks, and looking at the raid for positioning.
Turn 1
Pre-Split: there are 2 healers. You have no reason to contribute to healing, and unless your group's collectively under geared, you should not even be feeding at all. No reason to remove DPS from the boss.
Post Split: You are officially Co-Tanking. You want all the chances to mitigate damage you can, AND you want to kill th eboss to relieve your healers ASAP. So casting a spell is removing DPS from the boss. Not worth it.
Turn 2
This is such a face roll turn, but there are a TON of AOE attacks that hit Melee, you don't have time to avoid them while casting anything. Sorry, but no. Never worth it here. (When done the intended way)
Turn 4
Nope, Just no. You are doing way too much here to be able to afford not building enmity on everything you see. Wasting a GCD in here means your healers will likely die. If you can afford to cast stone skin on yourself, it's not likely to make any sort of impact on the fight. If you are tanking Double Dreads, you want to be blocking them instead of casting.
Turn 5
If your raid has died a lot, and your healers are almost dead, then yes. in the LAST PHASE, spam Stone Skin on yourself once your Cool downs are all expended.
Turn 6
The only time I can justify it, is the person who gets the Honey Debuff... Even then, it's probably not going to save him if the healers ignored him for too long. I however will be testing this myself, since i'm sick of my DPS getting killed by the incoming cleave.
Turn 7
There is just not much damage going out here... I can't always reach the DPS who is going to get Fire Balled with a Cast ability. The OFF tank is often on the other side of the arena, so i can't even help him after the very first add. So... if you can, try to? But it likely isn't a make or break thing.