As with all of the Neverwinter events, they shift in time each day. So eventually Gauntlgrym will be at a time that is better suited for you. Although, I feel that the Gauntlgrym events should be more frequent then they are. But they apparently don't like to have overlapping events.
If you can tell specifically which character used the exploit then should receive bans as well as character roll-backs to show that you do not tolerate the use the of exploits.
Since I started playing on Saturday, I have always had a Guardian in my group. But my sample size is not that large. From what I have seen it looks like the queue system requires at least a tank and a healer per group. Although as you have mentioned, I have also seen groups with multiple Clerics.