Dark Serge, you've admitted that your other characters are always at a much higher level than Magus starts at by the time you have a chance to recruit him, so I doubt you've ever given him a fair trial as a melee fighter. If the levels are equivalent, he's about on a level with Frog for physical attacks, and miles ahead of Lucca and Marle in all categories. And by the time he hits Level **, all of his stats except Evade (where he loses to Ayla) are as good as or better than everyone else's. His worst problems are that the Doom Sickle is much weaker than Crono's Rainbow or the second-level Masamune, and he takes longer to max out Stamina than the other heavy fighters (however, he maxes out MagDef much faster, which can be useful).
Yes, his magic attacks hit all enemies. So do almost all the other single techs worth having (the only exception I can think of offhand is Ayla's Triple Kick, although there may be one or two more that I'm forgetting), which makes that...pretty insignificant, to my mind.
And...cheerful evil characters disturb me. If you're capable of being happy and nasty, then you're beyond redemption. Magus isn't that. And he's a strong, independent, confident, intelligent person: all attractive traits.
Pardon me for saying so, but your objections against Magus seem to boil down to, "I don't like that kind of character, and the point in the story at which he becomes recruitable doesn't suit my playing style, so therefore, he sucks, and I'm tired of hearing other people say that he's all that, so I'm going to take him (and them) down a peg." I'm okay with you not liking Magus, but I don't think the conclusions you draw are justified.