my answere -
that might not be a bug, Devs told many times they dont wana made this game p2w ofc, since boosts are bought with IM why would devs allow mage debuff them (taking off buffs) that's like making that player wasting real money in game making the game p2w, if u mean by debuffs such slow m.speed, than smthing is wrong cuz even boosters can get that debuffs.
*sugestion*
for dont made that mutch p2w (im not a booster but wana try to help a lil the community), if booster die he will still with buffs + he just can use the boost again after the buff time finish ^^ my opinion (if isnt that mutch exagerated (YES IK IT WILL MADE DISADVANTAGE TO MOST OF F2P PLAYERS))