It did not used to count back in the early seasons. I'm not sure about now, it would be trivial to add a check for gear as part of the calculation. I doubt it matters much though overall. The output of blizzard's algorithm is a value called Skill so gear could easily be part of the input or not...
"First and foremost, the primary goal of the new Arena matchmaking system is to match players against opponents of similar skill, regardless of your or your opponents’ team rating. This means that once an estimated skill level is determined, you will more likely be matched against other players of a similar skill level. Please note that the estimated skill level is constantly being evaluated and will adjust based on each team’s continual performance. Ratings that are won or lost also take into account skill level, so that you will not suffer a high penalty if you lose against a team that is much better than their actual team rating." -Aratil