I'm not saying he should be your #1 pet or anything. If you don't think Nexus is worth it, don't buy him. At the rate that mages and rogues go through mana (especially rogues), it's nice to be able to switch him in for a while on grinding runs so you don't have to pot constantly. Pots aren't that cheap. The cost adds up very quickly. I like using him, that's all I'm saying.