While he would make a decent addition to a roster that is noticeable thinning(see Rumble), I can understand their recalcitrance towards bringing him back. The fact of the matter is, Lashley wasn't too great of a wrestler or too charismatic(which was no doubt related to his feminine voice), he was made to be a decent wrestler, and to be an over face -- the WWE bent over BACKWARDS to do this. Vince made a personal investment, with the whole feud, hair/hair match, bringing Trump in, giving Lashley a a major role in WM 23, his ECW booking, that fantastic match with Cena etc.. After all of that, he left. Why? Because of some shit with his girlfriend(who he isn't even with anymore). All the WWE got from that huge investment was one pay-off match with Cena. So yes, I understand their reluctance.
In no way is he comparable to Lesnar, who had legitimate career related reasons for leaving(though, he was douchy and unprofessional in his own way). Lesnar left because in just 2 years, he was pushed so hard, that he felt tired out. In just under 2 years, he had beat a bunch of top guys(Angle, Taker, Rocky etc.) AND headlined Mania for the belt. He was tired out. Also he hated the schedule, simply couldn't put up with it anymore and wanted to spend time with his family. If can't handle the schedule, you have little reason to be in this industry, let alone a TOP spot in this industry. The WWE was right to feel betrayed in that situation as well, but it was noticeably different.
