I’d hoped this would get fixed in the last patch, but apparently it hasn’t.
At the hero select screen, ARAM will regularly give only one team Tank options. The other team will only get Bruisers in place of Tanks.
This has happened in about 1/4 of my ARAM games, and the side without Tanks gets steamrolled almost every time.
Here’s 2 recent examples I remembered to screenshot.
https://i.imgur.com/bebkxod.png
https://i.imgur.com/H8uOF3e.png
https://i.imgur.com/AOM3Kbd.png
https://i.imgur.com/rKKbRcz.png
This problem is a recent issue. It only started happening when Brawl was replaced with ARAM.