Done! Only had 101 bounties left when it was my final trophy do it wasn't so bad at that point.

Does this game have competitive multiplayer?

No just co-op

Awww... :'(

One more character to level 70 and 280 bounties to go. I plan on switching to Normal, get my overgeared Wizard out and do speed runs for those.
Just need to finish this damn Monk now. 32 levels to go.

just play the bounties to level up on normal difficulty now

Rifts are actually faster for leveling up, I've found, especially on Hard and Expert. 

but playing rifts now and then playing more bounties later is slower for the platinum.

Took your advice and only did bounties for the last character. Still have 200 bounties to go, but I'm done with the classes. I can now just breeze through these on the wizard. 

Bit late to this thread - will probably plat this eventually.
Cant say I personally hunt for the plat, the trophies more or less happen eventually just playing the game (a lot),
I Think theres just two trophies missing now
My last class to 70 - Monk - is only lvl 45 or so and need to do more bounties (havent checked how many completed)

Usually I play it together with my gf and whoever on friends list thats online (not so often nowadays, most moved on to other games). Heard theres lots of cheating in this game but never seen it myself since I typically dont play with strangers.

I must say I really cant explain why this game is so fun to play, but somehow it still is.