Expanding on this thread a bit, So far I've seen the following group tactics work fairly well, IMO:

1. Stay close to each other - Preferrably the group leader

I've found that it's much easier for the group leader to call targets and get results when we're all fairly close to each other. Also, when we're spread out, what happens is we get pockets of battle forming with odds against us like 3v1 at times. If we stick together and the enemy splits up, we can get them in 3+v1s instead of the other way around.

Also by staying close together, it becomes easier for the group leader to move the group without worrying about straglers. 'Fall back to the east...oh shit look so and so is getting swarmed because they're cutting through the enemy trying to go east. If he/she was with us they wouldn't be getting swarmed.'

2. If an enemy drops, GANK THEM

The other day we were winning a group v group encounter, but since we didn't gank the people we dropped, enemies revived them, they dropped back and healed, and then came back at us in force. We had to retreat instead of wiping the floor with them. Luckily we found them again not to long after that, and this time we stuck closer together and ganked those we dropped. This time the enemy fled the field, and we got to loot.

Anyone else have more to add? Or maybe this should be in it's own thread. I don't know.