There are some odd set ups that can be really annoying for quad boxing shaman around 1400-1600ish rating.

Like this one I faced:

Fire mage, destro lock, MM hunter/Boomkin, elemental shaman, holy paladin

They were lossing perfectly, waiting for me to refresh groundings then quickly they run in, blow my groundings, run out, heal up, then rush in without my groundings up, one of my chars gets earth shocked, one gets counterspelled, one gets felpuppy and one gets sleeped/cycloned, then they focus nuke one by one. By the time I have grounding totem up again, one of my chars is dead and I didn't get the chance to nuke anyone down.

Quite frankly, it's an unbeatable set up for a quad boxing shaman (unless the other team sucks), but they'll lose against many other set ups so generally don't climb very high. I think the only way to beat a set up like that is to rush so they can't set up their focuses. But heh, I dunno. Rushing isn't a multiboxers strong point.

You'll meet less of those highly annoying set ups at higher ratings, that's true, but you will also notice people on high rating don't ever 'offer' themselves to you. They'll los good, and minimize the chance for you to nuke one before they can do anything. You'll have to keep your fingers at the ready and wait for the oppertune moment. But it's usually only a 3 second window in which you have to do your thing. Slack one bit and you'd lose.

Personally tho, I find 2 healer teams by far the easiest to beat. And there are plenty of those at high ratings. :P They generally don't have the healing power to outnuke your dps, they are easy to tunnelview because of that so lack in cc.

I'm currently on a new BG, Reckoning in EU, just started last week. the losses i had so far were against pretty good teams or annoying set ups. Fair game I suppose. Can't win them all and I am still slightly behind in gear anyways. But you'd be surprised to know I have it easier at 1700 rating then I had at 1500 rating. I started with 5 wins 5 losses, and ended with 23 wins and 11 losses (3 losses was because I messed up in one way or another but could've been easily prevented. :P ). So my winrating improves the higher I get. Until I'm in the 1700's where I usually lose a few because of pretty decent teams and slightly lacking the gear. But I've beaten 1900/2000 rated teams so, if I play enough games, I think i should be able to reach high ratings. That's my aim to do before wotlk. That and to get as much experience as possible so I make the start in wotlk the best possible way. ^^