Bunkers do great in early game, but in late game they are pointless, unless your opponent goes mass Z's in which case you fill your bunks with firebats. Or a bunker rush early game works great. Other than that, I don't use them much
Here is what you do with bunkers, make them by your resources so when you get dropped, your SCVs have shelter. lol i don't even do that. Make at expansions... yes. FB + Bunk v Zlings... yes. Bunk pushing... yes. Using them to make your base look better... no...!
No. In 2v2 u cant take the risk of teching, no matter the map. Players will hit u with 24 zerglings while u are still making ur first siege tank. U have to get M&M, zealots or lings early and outnumber ur enemy, and hit him with a force of 2 vs 1.