Communication is generally a key to victory when it comes to matches as you describe. Talking to your team, (not chatting, more like relaying messages), helps infinitely. Things such as pointing out enemy locations, where a push is occurring, where the enemy is defending, where you spotted enemies in what forest, ect. ect. All these things, while maybe obvious to you, might help teammates out who do not spot such things. This works both ways, obviously, as you want your team spouting out whatever information they have to help you avoid those nasty 3+v1 gank fests. Another important factor is knowing. It's just like G.I. Joe says: Knowing is half the battle. Know your own hero and know what heros your fighting. The more yo know what you can do to your enemy and to possibly get away from your enemy, and the more you know what your enemy can do to stop and/or kill you, the better. This means reading guides and possibly playing through matches as heros you generally are killed by to see how exactly they are killing you. Trial and error are the names of the game. In regards on what lanes to choose, ect. during the gank-fests, it's really fluid. As you described 'blob'. Trying to be on the opposite side of the map that you see enemies, or sticking with teammates is the general idea at that point. What to do in team fighting is dependent on what hero you're playing as. For instance, Warwick, (which you said you did fairly well with), is an excellent jungler, which can earn him fast gold and become a good early game ganker. By late game he becomes a carry and almost impossible to stop if he's done well with ganking early game. Generally just find strats and read up on the hero you are/wanting to play as so going into a game you already know what you're going to do. 3v2 ending in stalemates could have a variety of reasons associated with them. Things such as the 2 standing beside a tower, having the creep advantage, simply being stronger heros or having a better hero combo to fight the 3 all could affect whether or not the greater number decides to attack. LoL is by no means a shallow game, but once you get some experience under your belt things should start falling into place. Just don't let elitist jerks spoil your fun (after all, this is a GAME.)
Hope it helped.