There are many people who play the game, which was touted as allowing you to play in the way that you want to play. Many (most) are not optimal, and many may not fit with how you want to play, but if the people playing have fun then how is it your responsibility to crap all over the people playing how they want to? The number of times I see or hear of players who can't take the fact that they died and demand duels or "1v1 me bro" is astounding.
I myself have four sets of gear that I use for different conditions or play styles in PvP; Solo/duo ganking gear, solo/duo AP farming gear, group leading gear, and group following gear. When I get enough mats I might make another set for duelling - though that's not something I do often enough to really warrant spending the mats.
I'm going to list the types that come to mind and give a brief comment on them. I'm sure there will be more types listed and both intelligent and trollish comments by others later on. The purpose of this post is to point out that there's a place for (almost) everyone in the game.
Solo players who gank: Choosing who to gank (what target you're most likely to kill) and how to egress (get away) can be challenging at times. Sitting stealthed with a 1-shot FotM build on a run-back-to-the-keep-being-sieged line can also be very annoying to your targets. AP gains can be good, though very rarely great.
Solo players who 1 v Potato: This is "AP farming for dummies". Find players who are not as good as you, and kill them easily / quickly. There's some good AP to make here, though the major benefit is making awesome solo videos that promote your own awesomeness so as to collect more fan boys.
Solo players who 1 v X: Unlike fighting potatoes, solo players who fight two (or more) others who are at or around their skill level are in for a really good - and probably long fight. They won't make much AP as this falls into the duelling category, though my hat gets tipped to them.
Solo players who farm AP: Note that this is VERY different from the three above. Farming AP is a skill that is NOT the same thing as 1 v multiples (of any type). Farming AP is all about strategy. Knowing where to make the most AP, and how to make the most AP. Executing once you've finalized your strategy is rather simple. It still takes skill to execute, though the primary requirement for the AP farmer is dynamic thinking and applying knowledge / theory to situations in order to identify what to do in order to make the most AP.
Note that the builds and skills used will almost certainly be different for each of the above.
Small groups (arbitrarily going to say up to 8 people): For many of the longer term players, executing and winning fights with small groups is a lot more fun than in larger groups as it takes more skill and is more of a challenge. With AoE caps as they are, small groups just aren't able to take on full (or multiple) groups. Hopefully AoE caps change (are removed) soon so that those of us who prefer the style can go back to playing like that.
Medium groups (usually 12 to 16 people): Until recently (AoE cap introduced), the value in a 12-16 person group was AP farming efficiency as beyond 16 players AP is divided among too many people. With the new AP changes proposed for the Q1 2016 patch, I expect that medium groups will make a comeback.
Full groups of 24: Some people enjoy running in large groups, and with AoE caps as they are it has become a necessity in order to reduce incoming damage. The social aspect of a large group of friends in TS running around doing things together is a lot of fun. It's not very good for AP gains, though the fun of talking with and playing with all the people you've known and been playing with for many years can't be beat at times.
Multiple medium or full groups: Right now, the state of the game is such that running multiple large groups directly contributes to lag. This is the primary reason not to do so. There are VERY few groups and leaders who will purposefully do so, though it often happens that multiple groups end up in the same place due to it being a good strategic place to be (for AP or for map control).