first 25% is not a problem because first jack only comes in 75%

after that, it either jack every 25%, or after aprox 2.5 mins after his last brainjack cycle

side note: brain jack cycle is 6 WSs or after 1.5 min. Meaning your safe to tank it after it uses 6 WS(including failed attempts like too far away) or after aprox 1.5 mins after first jack

back to topic: So, if your unlucky that you got jacked at the 1.5th min mark OR the 6th WS, which happen to be brainjack, the 2.5min non-jacking cycle has started BUT you have 1 of your tanks still charmed for good'ol' 1.5 mins. Therefore after the 1.5 mins, your recovered tank will only have 1 min to damage LAC before the next charm cycle starts again. And in 1 min, you can MAY NOT deal 10-15% of his HP, and with prolly 1 tank still charmed, i think may groups will carry on kiting, and not doing any damage, which result in another jack cycle happening again.

i hope you get the picture.