Ok so I haven’t personally reached level 60 in this, the husband did but I just thought I’d share what he learnt from it. (Although considering the game has been out for a few years there are probably already tips about on this.)
C made it in two play throughs, the first starting from level 1 and reaching level 53 playing through on Hardcore difficulty. He did the second play through on Insanity level, and even then, with all that additional XP it was still a close call to hitting level 60 before he got to the end of the game. You need pretty much the same amount of XP to get from level 50 to level 60 that you did to get from level 1 to level 50. He managed it though, with about 5 enemies left before the last big boss fight.
First you need to do every side quest in the game on both play throughs. If you’ve never you won’t understand how tidious this can be enemies have an annoying habit of merging with walls when you use biotics on them add that to them having huge hit points due to the difficulty and this is not fun. Additionally all bases on the worlds are shaped the same, which if you think about it does make sense as the buildings are pre-fabs to make it easy to set them up on new worlds. In a game however this makes them really boring, there is nothing new to look at.
Second. Kill everything ON FOOT. Yes you heard me, on foot, you get a lot more XP from killing something on foot then you do if you use the Mako. (Plus on Insanity level your character can take more damage then the tank can.) But seriously creatures like Thresher Maws and Colossus’ give about 2000 XP each when you take them on foot.
Also as a side note it seems a lot easier to take a Thresher Maw on foot then in the Mako, you have a tendancy to over shoot in the Mako and driving around so you aren’t hit and aiming the gun turret can be awkward. Running in a circle around it shooting it with your pistol looked a lot easier (It also helps that your level 58 or 59 by this point).
Really though I think that’s it, if we’d realised the whole taking things out on foot gives you much more XP C would have hit level 60 a lot earlier than right at the end game. Still it is doable.