Time left to start battle with raid boss

Ok, so I have big problem. When we are in group, and we are gonna battle with let's say Tyranitar. We use raid pass, more or less at the same time. And then timer is showing time to start battle, so you have time to pick mons. My question - why the heck I have always like 2x more time than everybody?! Like they have 70seconds and I have 150. Yesterday my timer just count to 0 and everyone else just take down raid boss, so I just used raid boss. Does anyone else has this problem? Today I was able to raid, but just in time - I attacked with my mon like 2 times and Tyranitar was down. I'm really scared to do battles cause I'm gonna just waste raid passes.