How did I only get 1 ball? (Regice raid)
So I did my first Regice raid today. There were 9 people in the lobby. I went in with my Machamp army & Hariyama. So I have a 100% Machamp maxed out and four 91% level 30 Machamp. After the Machamp died, instead of using, my last Pokemon, Hariyama, I decided to back out and come in with a fresh new attacking group. I then came in with my 98% 2914 CP Moltres & 96% 2901 CP Entei and then Regice went down. During the raid I noticed a lot of people were using Lugia. It was actually the Pokemon the game was recommending me, but I was like nope. I was using, what I thought, were great counters and I ended up getting only 1 ball. It's been a long time since I've only gotten 1 ball. How the hell was that possible?
5 Machamp + Moltres + Entei = 1 ball? Hmmm...
FYI, I did catch Regice on my 2nd to last ball.

Answers
Your group was too large ... simple math says that IF you were to get 2 balls (20% damage) then the other 8 would average 10% each. I think it reasonable that some of them exceeded 10% ... Lugia is not a powerhouse but assuming they had futuresight it is a strong fighting move. Could also be the time you lost rejoining cost you a second ball. FYI I wish I could have a 9 person group size, in Bangkok we tend to have 16-20 trainers at every single 5 star raid. We dream of getting 2 damage balls!!!!!
20% damage --> 3 balls
15% damage --> 2 balls
5% damage --> 1 ball
100/9 =11% if u made average damage.
So 15% should be possible if the others use weak counters.
I guess your problem was that it took too long to change the teams. This let u lose the lead cuz the Lugias for sure didnt have to go in with a second one.
Just prepare 2 Teams. I have one Fire/flying and a Machamp Team. And even than it needs like forever to change cuz of lag. Thats why I prefer the fire/flying Team against Focus Blast