Most games have that kind of things. Remember much from WoW etc. And however much it sucks, I just shrug it off, its random after all. : )
Worst was when I did play World of Warcraft under the Lich King era. I was guildmaster, raidleader and main healer in a 10 man group. So many times did I heal alone or had it as main responsible as well taking care of the group. We just got in a new guy in the guild, and he was healing extra on Rotface. He wasn't really good, died early and all so I needed to keep it up. After many attempts on the boss did we finally kill it and we were super excited. I even more as the boss dropped a much wanted weapon for me, the Lockjaw, that would be a huge upgrade. Since we are such small group of people and friends mainly, did we have a simple roll if you need.
I was super happy until I realized the other healer, a shaman, roll as well and beat me by few numbers. For Paladins back then, 1h-mace was like the only healing weapon while shamans had more options, so I became super disappointed though I let the shaman get it as he won the rolls. Though he left the guild a few days later lol. Took me months until I got the mace again and won it.
Second thing was also under Lich King, as I did main healer did I have a hunter for those times when we needed extra dps. Back then if you used an character in one boss fight it would lock the character for the entire raid so was a lot to give up. But I juggled between my hunter and paladin for most of the time since my raid had hard time to fill the spots many times, though mainly I was healer. However, on Sindragosa, the second last boss in ICC, did I need to go hunter cause we lacked dps. We had managed to take her a 2-3 times before and I really wanted to play my paladin against her since she dropped Lost Pavise of the Blue Flight, which was a healer shield and the best one. Though so far it hadn't drop.
And after few attempts did we manage to kill her.
And the shield dropped. The damn shield dropped. And our dps paladin got it, something he teased me with for ages. I thought I was going to die. xD Though next reset we did her, did I actually get to play Paladin and didnt get the shield at all! It took a few times lol.
Just two random moments I thought was horrible back then but now Im pretty much chill about it. xD