Blitz is probably the most powerful tier 6 however it isn't OP as it requires skill to utilize it properly. Although some builds do have it easier than others when it comes to getting few stacks and keeping them.
In a group without any one being carried and everyone monitoring the kill count during quest you need to either plan ahead for the right moment to push the button or have the survivability to break off group and get your first few hits.
Blitz isn't the problem, people whining about it are the problem.