After reading the entire post I am left with the question: So? Why do you care how fast people farm or how powerful they become or the balance of solo vs group play (with a game that encourages community & socialising) when you're concerned with playing on your own, they have no influence over your game.
While I agree about not caring how quickly others progress this does create other issues some of which are simply issues on how it effects people psychologically and how the game is balanced. Starting with balancing issues, if there is a huge difference between two different play styles (group + solo) the devs need to pick one to balance around either making the other impossible or trivializing it. This is proven by the fact that right now T6 is very hard for a well geared solo player as it should be but groups are roflstomping it and personally I want the hardest difficulty in the game to be difficult no matter how I play.
The other is this feeling of what you get out of your time spent, for instance I was really enjoying playing T5 with my friends earlier we was killing quite fast and as a result getting XP and Legendaries at a fairly good rate yet then they had to go and my character isn't strong enough for T5 so I had to drop to T3 and even in T3 I wasn't able to clear as quickly as our group was in T5 meaning the rate in which I got XP and legendaries was cut by more than half and as a result the game suddenly felt slow and I got bored.
Personally I feel like co-op shouldn't give more reward than solo they should be more or less equal, if they was then when I left our group I still would of been happy in my solo game because it wouldn't have felt like the game had slowed down to a crawl but just going at the same rate. On top of this I don't even get why Blizzard feel the need to give incentive to play co-op, personally if I have the chance to play with my friends I will even if it were a little slower and there are people who would rather just play solo and they can to. Can't Blizzard stop trying to push people to play a certain way and just let them do what they want without feeling like there getting a fraction of the reward for it? This is the same as when they talk about boss/short runs and stuff because they want us to do bounties/rifts isn't giving us the option and letting us do what we want more important than having us do what they want?
The other is this feeling of what you get out of your time spent, for instance I was really enjoying playing T5 with my friends earlier we was killing quite fast and as a result getting XP and Legendaries at a fairly good rate yet then they had to go and my character isn't strong enough for T5 so I had to drop to T3 and even in T3 I wasn't able to clear as quickly as our group was in T5 meaning the rate in which I got XP and legendaries was cut by more than half and as a result the game suddenly felt slow and I got bored.
Personally I feel like co-op shouldn't give more reward than solo they should be more or less equal, if they was then when I left our group I still would of been happy in my solo game because it wouldn't have felt like the game had slowed down to a crawl but just going at the same rate. On top of this I don't even get why Blizzard feel the need to give incentive to play co-op, personally if I have the chance to play with my friends I will even if it were a little slower and there are people who would rather just play solo and they can to. Can't Blizzard stop trying to push people to play a certain way and just let them do what they want without feeling like there getting a fraction of the reward for it? This is the same as when they talk about boss/short runs and stuff because they want us to do bounties/rifts isn't giving us the option and letting us do what we want more important than having us do what they want?