The second wave of sentinels appear to be a major issue on wave 45 ! Whenever I play insane or above our team gets killed by these enemies 
My characters are level 16 to 18:((
Have some trishots ready and spread out?
Maybe a couple decoys?
Haven’t played much insane+ yet but this is what comes to mind.
Its a shame this game already revolves around sentries n tri shots for higher difficulties…and gl spamming by jd…pretty much just use those for sentinels…shouldnt be called horde now as this shitshow is anything but.