Unless they expand the tiers again or implement a more comprehensive rework (Don't hold your breath!), 3v3 will only continue to get harder.
If you are in a clan that cares about Siege, there is no better training ground than 3v3 because it forces you to use a wider range of toons, which helps you learn more about team synergy.
If you want help, we can help you put teams together based on your Roster. Over the years, what I have found is that a lot of people like to complain about 3v3 w/o actually putting in the work to gear their teams correctly, figure out how teams work together, and pick the right fights.
I am a long term low-spender and I can climb all the way to G4 when I want to. It is a lot harder than it used to be, so the only time I bother is leading into PR CVC. This week I am G3, but will fall to G2 because I am running 1-man teams. I will promote the next 2 wks and be in G4 for the next PR.