Yeah everytime I host I use something like 'pros only'. Never works.
This is exactly the problem - if you host a game called 3v3 pros or 3v3 no noobs, whatever, you will struggle to get players. I myself play with friends on an almost nightly basis and there is nothing worse than walking over another team, this is where demigod fails, it's pure tedium. However when we get a challenge and the game is hard fought and down to the wire, it kicks total ass.
So what's the magic solution? There isnt one. If i was playing with 2 friends for a set 3v3 team, i have considered splitting us up as we're all quite good players, but what then? One is stuck on a team with potential noobs and the experience is just plain cancerous.
The only solution IMO is to put in a completely random team option and i guess Panthenon is this to a degree, but i never play Panthenon as i dont dig 2v2's on 5v5 maps.
Dawn of War 2 has 2v2 and 3v3 gameplay where you can join as a random, but if you do go in solo youre still mostly going vs set teams and getting smashed if your teammate isnt up to scratch. There's no magic wand fix unfortunately. Nor is there such a massively huge playerbase to sustain all kinds of variants - ie 3v3 good players