I just can explain this locations of clanhalls like -
If we have 2x2 PK. Any newbie can reraid sentinel... EASY!
But you must be very, very fast, very skilled and vey protected to try
raid Cobar.... 2x2 PK....
Seems no difference, but this small thing like place are will deside how much your chances to stay alive.
Well... I think that depends a lot on the players and classes... if there is no ranger in cobar, you can hide quite easily in middle of the plains. And if there is no priest to heal the horseman also reraid can come easily. If there is priest for Guardians, reraid against Guardians also becomes quite difficult.
Or you forget the time Adelin was Counsellor? Guardians reraided Cobar quite easily, especially when Adelin and Menuoki were there.
And well... about the academy for PK... everyones been there already... I personally became quite fast because I always made classes that didn't have healing, word of recall, summon, or anything of the sort. Consequence is, I had to move my butt very quick to run while blinded back from whereever I was to Palanthas and heal myself.

Or even I had to move very fast to hunt people down. I myself think you shouldn't consider it a disadvantage that you have to face these conditions, it will make you better in PK no matter what happens now. To ask for these conditions to cease to exist is, in fact, to condemn part of the game. The fleeing/hunting part!!! Which is why rangers are so cool!!!

Which is great part of usefullness from clerics of Morgion and their damn fatigue!!!

Which makes gate so usefull!!!
Ok, ok, I over-react a little... but I can't help it