Hachoo-

I was similarly disappointed to find out this unbeatable strat would work! So I had to adapt to exactly what you're talking about.
Take it slow. Pull those two guards up to the top of the ramp, and have your shamans parked on the aggro side of the "color change" on the ground. So in other words, stay just on the beginning of the downhill.
Kill the two 57/59 guards. Drop grounding totems before the 2nd one dies.
Now begins the "exodus". The dragon rider will come down and yell, and like you said the dragon himself will attack you from 150000 yards away with fireballs. Let him get four off, and when the fourth is flying run about 20 paces downhill and drop your new totems.
I like to make use of this time to chain heal, or mana-spring mana back up, too, because dropping one grounding totem every 44 seconds allows you time to regen a lot.
When you get to the bottom you're going to get 41 yards away from the dragon rider, all the while dropping grounding totems. You're probably going to drop grounding totems twice in one spot (in fact that's ideal)
As soon as you drop your last batch (and hopefully drop your others like 3x Healing Stream 1x Mana Spring 1x Fire Resistance, as well as 5x ToW) then go ahead and zap the dragon rider's butt off.
When he's at like 40% you'll get the "Vazruden descends from the sky!" raid warning message, but the funny thing about shamans is by the time the dragon starts descending, you're going to have 5x lightning bolts already *descending* on the dragon rider's face.
So he'll be dead before the dragon is even combat-ready. Now you have to drop 5 more grounding totems and get away from them. Fireballs that the dragon shoots while on the ground are the napalm kind that leave that dangerous AoE patch.

How to kill the dragon? I had one alt with an elemental at this point, so I was able to use that. I don't know how you're going to do it because he's much tougher than the other guy and likes to swat/explode your face/flamethrower all of you.