There’s no evidence that Anet cares about this issue, so:
- Don’t pug in a group with more than 1 member from the same guild.
- Enter the instance first so that if you’re kicked the instance is wiped for everyone.
That – although grouping might get slightly difficult if everybody insists on opening the instance. 
In regards to teaming up with a guild: If something goes wrong, you will be blamed. Simply because you are the filler. It really doesn’t matter if you screwed up or not.
If you pug a lot, you will get a feeling when it is a group you don’t want to be a part of.
This goes for the group setup as well as the attitude.
One indicator I found rather useful when (partly) grouping with another guild is to see if they are capable of a simple “hello” and basic strategy communication. As mundane as it sounds, this really helps to sort out bad apples.
Also, if people put up a lfg that gently hints towards an addiction to capital letters and exclamation marks, you might want to reconsider joining.
It is an exploit, using Shortbow. They use it to teleport where they shouldn’t be able to go and skip the whole dungeon. Some kinda of jumping puzzle. Use it at your own risk.
However I remember seeing a post about a Dev saying the “jumping puzzle” were not exploit, but I wouldn’t trust that.
Well there was (is?) a partially completed jumping puzzle after you finish the boss.
For the current thief skips – as they are practised/tought – I highly doubt that any dev would claim that this was working as intended.
If it was jumping puzzle, it would (theoretically) be doable for every class and if this is not seen as exploiting, then everything from the snowflake incident to the linen farm can’t be considered exploiting from my point of view.
My advise to OP is to stay away from this, unless you want to risk a righteous strike of the banhammer.
This and similar skips for Arah are one of the main reasons why dungeon sellers are frown upon (another reason is that little bit of envy, because honest soloing is actually quite skill-based ).
In regards to AP requirements:
AP does NOT equal dungeon experience. Everybody that actually IS experienced knows this. It is nonetheless a basic indicator if your fellow player has some experience in the game.
The basic guideline I follow for explanations:
AP < 1k = explain the mechanics unasked
1k < AP < 2k = ask if they want explanations
> 2k = explain if I feel that that (someone in) the group would benefit
Always keep in mind that you can learn from anyone, independent from AP. Quite a few high-AP players like to forget that rule, but I happily remind them.
In regards to LFG tool usage (and I think there has been a post somewhere on this forums in more detail about this):
- Px: Don’t care about level or experience.
- Px, 80: Level 80, don’t care about experience.
- Px, 80, exp: Level 80, know the core dungeon mechanics.
- Px, 80, speedrun: Level 80, know the dungeon in detail, proper equipment (e.g. PVT might improve your survivability, but at the expense of your teammembers).
Note: If I look for a specific class, I will add this in description.
All this doesn’t save you from bad apples, but that’s the risk you take in pugging.
And if I’m in a group with people that obviously lack manners (uncontrolled swearing etc.) or are unwilling to at least listen to suggestions, I leave.