That is a nice background and rules for Arctos. It is definitely not overpowered, and I like the wing cyclone, fluffy and appropriate, yet not too strong. I think you could make heartseeker more of a lance-type weapon, with maybe +1 strength or +d3 attacks on the charge? The model is also excellent. The bloodthirster wings look great in that position, much better than on the actual bloodthirster model.