Think of it this way, if you need polygons in a spot so that you can get this important detail that can't be conveyed with texture, like the mouths of hydreigon's heads, or the spiky teeth on said heads, then use polygons. If you feel that something needs depth that you can't convey with texture, use polygons, if something absolutely needs to have a decent curve in an arm or a wing, use polygons, but use them sparingly If something needs to have a perfect curve and you feel like you should add 20 edge loops to make it look perfect, don't.
When we talk about polycount, it's less about the overall number and more about the use of those polys.