It is classified as a Mystic technique by most players. It's a bit bizarre, but it is not considered a magic attack, nor a melee attack. Rather, it's just a long ranged skill would probably be a better way to put it. Thus, I don't think it's blocked my GTB. It might still be, but... eh. My money isn't on it.
On another note, INT is generally better than STR in the case of SD. Why? Because INT will always give a +50 damage per INT, while STR's bonus are not worth noticing until it reaches in the 10's, and you'd have to get your strength pretty damn high to truly out-power INT in worth. Furthermore, it is a lot easier to get DEF than it is MDEF, as most classes don't use an abundance of INT, and there are more physically DEF-powered monster than those with a lot of MDEF. Thus, INT is often a focus point unless we deal with an Ice Pick + Endow combination, as it doesn't seem that endows effect the INT section of the attack. o.o; -shruggeth- In that case, STR is superior without a problem. That, and when you start adding megs to the equation, STR starts to over-power INT.
I'm not sure, but I don't think the status effects will be put into the SD, even if it is primarily STR based. This might be wrong, but I've never seen anyone do this, so I doubt it would work. o.o