What are you trying to do when you use the LFD tool?
"Find a group" is the simple, useless answer. It only leads to the question, "What is the group for?" So let's ask that, what is the group for?
I'm not the first person to suggest that LFD have style options, such as "quick badges" or "reputation". But I'm suggesting those again. I don't think they go far enough. For players running BC content, they may want a group with only level 70s, in order to get justice points from bosses. Add a "level 70 only" option. A similar option may be useful for players who want to stay at 80.
Another option could be "incomplete groups", meaning that if there is a shortage of DPS, which I've seen at some levels, a group may be formed with only two DPS rather than the usual three. The group would be able to start the instance but would stay in the queue, exactly like if you had formed a group and a player left. This would allow groups to form much more quickly in low-population levels and content, such as in the level 70 and 80 heroics. Usually it is a healer which is missing, but I have seen groups with a healer, tank, and two DPS, but unable to start because of a third, despite being fully capable of completing the instance.
Since this could result in many DPS being dropped into partial instances which they might not want, add an option for "no bosses dead", so that players are not dropped into incomplete instances and then possibly saved to a failing group. Or dropped into an instance where they boss they needed is already dead. However, add a slight bonus if players join an instance in progress, so that partially-cleared instances do not become impossible to complete due to lack of players.
Unfortunately, this may end up adding so many new features and options that the tool becomes unwieldy or fails to form groups. If I pick "speed run" and "no bosses dead" am I going to be stuck waiting forever? What if I pick "only level 70" but not "partial groups"? Is that an option? The way Blizzard displays this options and features would matter, whether we can see all our options and have some sense of how they will affect the speed of forming a group, as well as how they might interact. Having a long checklist of options may result in too many players segmented off, which may mean that Blizzard has to make some mutually exclusive or inclusive, so that "level 70 only" mandates "partial groups" while "speed run" is not an option.
In the ideal situation, there would be such a perfect ratio of tanks, healers, and DPS, and in a sufficient total population, that no options would be needed beyond picking a role and picking a location. If we don't like the group we get, we can drop and try again, with little time lost for anyone. Sadly, we play in a world of shortages, which reduce our flexibility, so we need tools to compensate. We're left picking between a lot of imperfect fixes.