So I've been running a lot of randoms lately and I've come across a lot of bad instance groups. Most of the bad groups have very distinct characteristics that point to them being bad and that you should run for the hills if you end up in these groups:
1. If your healer has more health then your tank and both are in the proper spec/gear.
2. If your tank has more spell power then your healer...and your tank isn't a paladin.
3. If your healer disconnects after a pull, your tank pulls anyway and wipes but still insists on continuing without a healer.
4. If your tank insists that they know the instance and has run it countless times...yet they keep pulling unnecessary mobs and/or they get lost and lead the group into a dead end.
5. If your tank dies on the first pull and then states that they weren't in the right gear/spec which is why they died. They then proceed to switch into the right gear/spec...and die even faster on the exact same pull.
6. If your tank keeps needing on all the gear that drops and claims that it's an upgrade then upon inspecting them you realize that they are actually wearing the gear...even if the drops are cloth/leather.
7. If your tank/healer repeatedly rolls dench/pass on greens that are obvious upgrades and when you bring it up to them they get mad at you for "telling them how to play their class."
8. If your group is doing so bad that a hunter mentions that their pet can tank, your tank/healer agree wholeheartedly and want to try it out...even though the hunter isn't BM and they don't even have a tanking pet.
9. If your healer dies every trash pull and your tank yells at any cloth wearing class for not stepping up and healing when the healer died...even though the group consists of a lock and a mage.
10. If your healer is out dpsing everyone in the group without actually attempting to dps. For example: thorns, ret aura, or disc priests reflective damage.
If you've had one or more of the above...then I hope your repair bill was not too high. If anyone has some more signs that your group is doomed to fail please post them. The better prepared you are to recognize a fail group, the better your chances are of avoiding them.