I don't think Edward and Tellah were that bad. Sure, Edward isn't too good in battles, but his last harp (in the SNES version) does a pretty good amount of damage, and he seemed quite alright in FFIVA too, when you can choose your party members. Besides, he stopped being a cowardly spoony bard and developed as a character during the game. Him using the Twin Harp to save Cecil and others from the Dark Elf was one of his great moments.

Tellah was good as a character, and he had loads of spells you won't get otherwise, until a lot later. The problems with him were that he was quite weak, and he had only 90 MP. That won't let you heal much, and you'll run out of MP very quickly. His magic power didn't seem too great, either. However, it's a tragic story he has, being blinded by so much anger that it cost him his life. He was still the first character in the game to cast Meteo, though.