What kangz said. The feet should be attached more strongly and the body diameter should be bigger so that it occupies more of the space of a bounding box that includes the feet. (Alternatively, if you prefer the structure to be slightly slimmer than on the concept, you could also make the feet extend less. You would also want to make them look less heavy in this case. But even then, a slight increase in diameter couldn't hurt I guess.)
Apart from this there's not much to critique. I like the simply shaped lower body but maybe you can think of some additional details on its lower end.
Regarding the poly count, I assume a lot of those triangles are used for rather small details such as the attachment between the two parts of each feet or the deails on the topmost part of the Drill. I guess this could be reduced further with good use of the normal map. Maybe try to aim for 3k tris, otherwise 4k would be fine I guess.
Seeing your latest reply, have a look at the Wikipedia article on bounding volumes. Currenly we use bounding boxes (with a square footprint) for both collision and hit detection, so parts sticking out of it could clip into walls but couldn't be hit and areas inside the box that aren't filled with geometry could still be hit. We are working on upgrading our engine there, but we don't yet have sufficiently stable results that we could base our assets on. Therefor the width of the body of structures like the Drill or Reactor should roughly match the width of their stand. This is also the main reason why I wanted you to shorten the Telenode legs. (The other reason was making it fit into small niches even if we switch to per-polygon collision detection.)