User blog comment:TeaIsExplosive/Pick-a-lane-queue/@comment-5441738-20130208172552

The main issue with queuing by role is already present in World of Warcraft. Usually, for a five-man dungeon, you'll want a tank, a healer, and three damage-heavy characters. The problem is that that actual ratios of who does what in WoW is not 1:1:3 as would be ideal but closer to 1:2:50. A healer will get a place quickly, DPS characters are waiting for at least twenty minutes, and the tank gets in as soon as he hits the button to queue. While these ratios aren't anywhere near as off-balance in League as they are in WoW, that issue would still be present.

A second issue then arises: What if the overall meta changes concerning how teams should normally be balanced? A system too strongly focused around Toplane-fighter/Jungler/AP-Mid/ADC/Support may be too static to represent the changes that the community as a whole want to make. On the other hand, a system that's not tightly defined enough could prove otherwise problematic as it approaches uselessness.

This is, overall, an issue that should be dealt with somehow, but there isn't a ready solution that I'm aware of.