The importance of your stats depends much on your template.
I put my thieves in factions, so more often than not I am being ganked by large groups. I find that the very same thief template I used in the pre-AoS years carries over today, though trading Arms Lore for Ninjitsu (pre-AoS you required Arms Lore to disarm). A straight wrestle/parry thief, with some resist squeezed in or swapped around with parry. But if you don't plan on having an entire team after you, you can get more creative with your template, like Nexus or the temp you are currently working.
Anyway, back to stats. 100-110 base strength, some HP and str bonuses on your suit, and a strength pot with 50% EP will set you straight, there. Aim for at least 130 HP in human form, 150 in wolf.
If you are going to use parry, keep your dex up. Especially if you wont be able to resist curses. Fall under 80 dex and your parry will go to ****. Again, however, you can get a great boost from agility pots and EP. Rely on that.
Intelligence is where you'll need a good base. There's no pot for this, and not many armor pieces with intelligence that's fit for a proper thief. You'd be surprised how quickly ninjitsu moves will eat your mana. With my suit I try to have around 80 mana, with some bit of MR. Smoke bombs, wrestle specials, shadow jump, mirror images, animal form...all uses mana.
