my fave areas for leveling:
cbed - recoboxing
cca - merils
cr8r - ma4c 2 the lizards then rm
^^^^^^^
these strats are not only braindead but are the fastest leveling methods in the game. the former work best as a cast and arm unit (kingz bonus), the later one worx best if u like to cast gif all day and hide behind rox (if you are low level/not alpha enough to face baboota).
exp/hr these methods are very consistent and fast. just /lobby after the last enemy dies for quick rm.
things you should watch out using each respective method:
cbed - kill all "active" recoboxes, then exp steal off the ones that aren't "active". don't corner yourself against a wall or bother stealing off recons, you will just get killed. demons mex are great here. good exp/hr, make sure you are using arm units as your accuracy will be shit.
cca - actis first meril on one side, doesn't matter which. mind the traps. don't move up to far, door snipe if you suck. if you're cast, go ahead and use fts since it will lower their evp, otherwise fs or sq is decent (just s, dont ns bc it will dmg them more). exp steal till one dies, then move onto the next. good exp/hr, esp as ra.
cr9r - watch for the bab since he is the biggest threat and will disrupt you the most. i have a good and secret strat for the lizard part but i can't share it as it is secret knowledge but you can complete it faster that way. see if you can figure out yourselves (fo only). if you are ra or hu i'd recc exp stealing instead of this method. crazy exp/hr if you are fo.
note that i don't recc mu3(4): at lower levels if you aren't godly or have gear it's an issue and will just take longer. once you're higher level or have decent gear or are at a decent level then i'd take this on. there are some rng elements that make this more annoying for lvling, it's more for hunting/lvling instead of pure lvling.
these methods are much more consistent than MAS, they also don't require perfect stunlock (while, like anything, ARE more efficient if your inputs are good and fast).