Hi ... I disagree with the OP.
I PUG 100% of the time these days. I bought a Jester just for fun. After 82 matches my W/L is exactly 1.0. K/D is also about 1.0 ... I am still working on finding a really effective build for this mech. (On the other hand my W/L and K/D with my Jagermechs is higher likely due to the effectiveness of ACs at the moment).
I also find that most PUG matches (which often have pre-mades on one or both sides) are won or lost based on the relative "stupidity" of the opposing players and the ability of a team to take advantage of local numerical superiority.
1) Keep in mind that an advantage of 1 or 2 mechs is often sufficient to win the game especially if the team decides to push and can take advantage of significant local numerical superiority. Four mechs together can burn down even an Atlas very quickly with focused fire.
2) Some of the bad tactics used:
- Some folks like to go out to find the enemy. Usually they succeed and die for their trouble.
- Some folks like to peek over a hill or around a corner or through a choke point (crater entrances on terra therna ... ridge on frozen city) ... this is dumb ... usually there are 3 to 6 opposing mechs on the other side of the hill - they all get a shot and you get one. End result is your team hit points go down a lot and theirs go down a little. If you are going through a choke point - push all together and focus fire on ONE opponent at a time and burn them down.
- Scouts often think they are invincible ... yes Spiders can be hard to hit ... everyone AIM for their LEGS ... they die very fast when they stop moving. Same goes for every other light. If you want to use lights to distract the enemy (and it can work REALLY well .. do it just before your heavies start pushing ... dying to no purpose harassing the opposing team by yourself in a light mech is generally useless.
- Splitting up so that the groups are too far apart to support each other. If the opponents have not done the same then you will most likely lose since the other team will wipe up one group and then the second.
- lack of awareness of the mini-map about where your team mates are.
- Desire to get the kill resulting in poor game play. Some folks like to get the kill shot and try to solo/duel opponents and complain when someone helps. It can be a lot of fun to solo another player ... but it allows the opposing mech to do twice as much damage before it dies. When multiple folks kill the opponent it dies faster and does less damage leaving your TEAM in better shape.
- Not finishing an opponent when the opportunity arises. Too many folks let that badly damaged but fully armed mech retreat. This mech needs to be primary when it pokes its head out ... it is a PRIME target for light harassing mechs that can get behind the enemy and kill these badly damaged opponents. Too often folks have let my Jagermech live with red torso sections while I continue to pour damage into the fight from a distance.
- Target selection. Depending on the meta ... certain mechs are more effective than others and REALLY need to be primaried. At the moment, I would put Jagermechs at the top of the kill list due to the effectiveness of auto-cannons. There are just too many Jagermech builds which put out a ton of dps at no heat from range. 4 x AC2, 2xAC2+2xAC5, 4xAC5, 2xAC10, 2xAC20, 2xUAC5, 3xUAC5 ... if you aren't blowing up the Jagermechs on the opposing team when you can ... you are doing your team a dis-service. Same goes to some extent for the SHD with 3 ballistics slots and any mech that can fit 3 or more ballistics. (The same goes for some Cataphracts - especially the IM).
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If most individuals play smart on a PUG team, support their team mates, focus fire and generally stay together then PUGs can be extremely effective. If you end up on a team with a 4 man pre-made that knows better and wanders off on their own leaving the others to disperse ... you will likely lose despite the pre-made.
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One final comment, sometimes bad play can be turned to your advantage ... I was driving a Jester and I noticed a raven behind our column on Terra Therna as we bypassed the crater ... I went back by myself (dumb!) to see whether they were going to base cap. The raven was joined by a cicada ... I exchanged a bit of fire and then 4 or 5 other opponents popped up beside them so I ran. I ran dodging into the crater at the bottom taking lots of fire but chased by 4 or 5 opponents trying for the kill - then ran back out of the crater along another valley that lead directly to the main group of my team. I died in the valley but not before the 5 opponents ran into my 10 team mates ... and died for their trouble. They got the kill they wanted and my team ended up with the win

... since it was difficult to overcome a 4 mech advantage.