Was reading the forums today and found a post that discribes our problem of last night, with the electrical spikes hitting through the shield.
As i understand it its caused by the DPS getting the agro from the TANK, wether a agro dump happens or not if the TANK is hit with the double destruction debuff he generates less agro.
When the DPS has a Burn active at the time the tank moves out of range (to run around and plant the electrical spikes it targets the DPS.
In last nights event i believe it targeted myself cause i was at the Shielded possition both times.
Also it might go for his previous target (the other TANK who might have switched Boss by now ) (info by talking to marrt).
So recommend for next time to use Target of Target (alt F) and perhaps have both tanks on the outside when Offenive measures hit. and the DPS on stormcaller drop there Agro before moving.
other then that i believe we are on the right track.(vid guide here)
and the tanks don't need to switch bosses :D ( hense why the tanks didnt have much agro )
1.Tanks don't need to switch, if u got your healers compensating for the Corroded armor debuff, sure.
2. agro loss can also happen from the Dubble Destruction debuff. (Tank should stay close to the DPS's and move behind them when DDestruction hits automaticly giving the debuff to the dps)