This is going to be a very broad thread on exactly what the title implies. Let's brainstorm some ways to mitigate grinding. In other words, let's come up with ways that progression can be slow, satisfying, and not grindy (I'm looking at you DCUO T4 armor)
Edit: DCUO means DC Universe Online, it is a superhero MMO based in Gotham and Metropolis.
In DCUO you would earn Marks of Triumph to purchase endgame gear. This endgame gear would raise your Combat Rating, which is a measure of how effective you are. Once your CR (as it is called) reaches a certain point, you unlock more missions to give you some more MoT (Marks of Triumph). each new set of missions would be called a Tier. The issue with this was you were given about 4 solo missions, 4 2 person, 4 4 person, and one or two 8 person missions per tier. The issue starts to show itself at T2 (Tier 2). At this point in time, it requires approximately 175 or so MoT to get some new gear. each mission would provide you with 5-10, 50 or so at most (The exact numbers are not important). once you hit the next tier, the amounts needed to go up rise so exponentially that the past content is no longer worth your time to even run. T3 it requires about 1200 MoT per piece of gear.
This tapering of content meant that you would grind everything available to you until you are a) a master at it and b) tired of it (at T4 the bordom comes after your 2nd or third piece of gear, where a one hour 8 man that only rewards you once a month gives you 1/2 the MoT needed to get some new gear). So yes there was plenty of entertaining content, but the fact that anything but your tier of missions is pointless really makes it feels super grindy and have a sense of confinement. What i mean by confinement is it made me feel like i was part of a routine, log on, do solos and duos, try and get into a 4man log off and try again tomorrow.
Don't get me wrong, DCUO is my game of choice until TPP launches. It has caring devs, frequent content updates (1/2 of which i will never see until i complete more endgame). I find it quite fun, and quite super, but it does show really well that tiered systems can have a real weakness.
I think CoH did grinding quite well, at any point in time, any enemy could drop a purple recipe (The equivalent of a new piece of gear in DCUO) or you could just go out and buy a recipe from wentworths or the black market. You could run your missions, taskforces, badgehunt, do AE. anything that was at your level and potentially get a recipe or salvage. It was not this "I know everything about these four missions, time to move onto the next four for 2 months" it -to me at least- was more of a "Hmm, badge hunting.. what nex- hey look a LGTF is forming, sure why the heck not?" I never really got this feeling of confinement, as a matter of fact, i played from launch and still missed probably around 24 hours worth of content at the time of shutdown.
That's one of my ideas for migitating grinding, stay away from the way DCUO is handling it. I'd bet, in about a year there will be t8 gear out there, advancing the story, but getting evermore grindy. Tiers are great in theory, but people will eventually be categorized by it and restricted by it.
Again, this is my opinion, not solid fact (However the facts themselves are actually facts haha)