Since I don't think we have Dire Tigers as mobs, but the more flavourful Saber Tiger, I think that the sudden appearance of one in a random transition area may be a bug resulting from the Tiger Tribe stargazer PC's custom companion. Happened last night (GMT) at the transition that then led from the Freshwater Springs.
I've seen a few Dire Tigers. They are thankfully rare, but I don't think they're a result of bugs.