At lower levels (pre 30), you're going to have threat issues, which will change once you get your jobstone (and in WARs case, a tank stance) that makes things easier. Provided you got a handle on tanking at this stage, you could spec into STR from the onset, but if not I'd suggest staying in VIT until at least lvl50. By that point you should be attuned enough with tanking to then feel comfortable making the switch.