Couple of things:
If the ranking system is an element which is effecting latency, then remove it. The ranking doesn't really reflect how effective people are in game anyway, as many play their dual more than their main. If you should have such a system, which is updated weekly, base it on player contribution, irrespective of main/dual activity.
Similarly, go back to the maximum of 3 account logging at any one time.
Although I love it, remove the auto macro system.... let's go retro and go back to old school methods... but only if this is impacting on latency!
As players invest serious time and in some instances, serious money via L2 store in the game... make sure that the 'mechanics' are fit for purpose.
And finally, really listen to the gamers'.... majority have been in game 5, 10, 15yrs.... we love the game, we just get frustrated at the 'stuff'.
Oh.... and final, final bit..... increase clan sizes again!