Groupfighting takes skill lol, knowing how and trying to read your team mates mind is a lot harder then 1v1ing, 1v1ing is basically just who uses this games gimmicks better than the other, while groupfighting is a combination of working together, communication, game sense, positioning, etc. Some people are great groupfighters and not great duelists because they understand groupfighting and focus on it/ develope their style to do so, which might not work out in a duel. But seeing as this is a team based game, groupfighting is more important too. I would rather have 10 people who understand how to groupfight than 10 duel heroes in a fight.
Though I agree somewhat, but to be a "duel hero" you basically automatically are a good groupfighter. You automatically have the skills to be a good groupfighter by being a good duelist, however being a good groupfighter does not make you a good duelist. Top tier dueling is all about game sense, positioning, and reading your opponents. Any good "Hero" worth his salt can read multiple opponents as easy as he can read one. Take a look at Jackie real quick. Hes a great duelist, but lacks communication. What makes his dueling so great though is how easily he reads his opponents and adapts his style. Every time ive FT7d him, I always start out with the early lead, only to get rolled out of nowhere once he adapts to my style and learns to read my movements. Every duelist can read opponents and adapt like that, its just the better a duelist you are, the better you are at doing just that. Thats why alot of great duelist's skills seem to translate into solid groupfighting without fail (i.e Jackie, Tammo, Russianfury, etc), so I think ill go ahead and say id rather have 10 duel heroes than 10 people who understand how to groupfight.