The blur'd bladesinger is only as overpowered as the enemy's tactics. If its a party wipe except for the bladesinger, that doesn't make things better. The damage output of a bladesinger is small enough that they don't really qualify as a large threat, and if you're in close, the bladesinger can't be firing off fireballs like an Evoker could, or function as a good tank.
Every game is different, and every GM has situations they have trouble coping with. My GM wouldn't have an issue dealing with this kind of issue. This idea that people are throwing around, where you casually have the ability to calmly cast a spell with enemies that for some reason or another always start far away is mind boggling to me. In fact, I find it extraordinary. Dungeons tend to have rooms, corridors that take a single turn to traverse with a charge, or obstacles like trees or some other terrain features in the way. And don't forget traps! Open fields are the exception in my games, not the rule.
Every game is different, and every GM has situations they have trouble coping with. My GM wouldn't have an issue dealing with this kind of issue. This idea that people are throwing around, where you casually have the ability to calmly cast a spell with enemies that for some reason or another always start far away is mind boggling to me. In fact, I find it extraordinary. Dungeons tend to have rooms, corridors that take a single turn to traverse with a charge, or obstacles like trees or some other terrain features in the way. And don't forget traps! Open fields are the exception in my games, not the rule.