I think it isn't without its problems, but I disagree about what the problems may be. I personally use Guildleves not as a way of leveling, but as a means of income; I do them for gil and to change up from the standard grinding. I do however feel we need more variety in Guildleves, as they all boil down to "Kill x amount of enemies." There are all sorts of different leves they could do, like perhaps a racing leve where you race an NPC from camp to town, or finding an item based on a set of clues about the surrounding area it's in, etc. Just something different.