Under Hasenhuttl, our performances put us in the 7th to 10th zone, ergo its simply untrue to say we need "serious changes to make us a top 10 side".
Of course, that doesn't mean we should stand still and not seek to improve the squad (to answer your "why bother?" question). Yes, we've got a squad that is putting in performances that makes us a top 10 side, but we don't make it easy for ourselves. Improving the squad will obviously (a) help us keep pace with the other teams in our 'best of the rest' peer group and (b) make it easier to maintain our top 10 status.