Well, from my own experience, this is quite normal. You didn’t specify which ranked, but I’m guessing you mean TL.
HL is more even because groups can’t queue and players lock heroes in order. If you’re not queueing in a group I find this a much better experience. Yes, there are trolls, but there are more trolls in TL.
TL is extremely frustrating, but keep in mind that the troll could also be on the enemy team. First lock Nova, or last lock assassin after you have 2 assassins and 2 tanks is quite normal. I’ve tried to prevent this by picking a healer earlier, as nobody in random teams seems to want to heal, but it happens sometimes that the last person then locks a healer as well. I guess they’re afk watching porn.
The best way to get around all this nonsense is to play TL in a group of 5. Group of friends on voice chat is of course best, but even if it’s randoms, they will be less likely to troll, or you can kick and report them afterwards.
Anything but 5 man team is a lottery, even if you’re 4 good players, 1 troll can easily make you lose.
If Blizzard would prevent trolls from joining TL it would be a fun game. Unfortunately it’s almost always frustrating, either for you, or for the enemy. Perhaps 1 out of 10 games of hots feels fair and fun, the rest are either bad losses or easy wins.