I recently leveled my heritage armor team through everything, actually just hit 120 yesterday.

You can get from level 100 to 108 just doing the rares and the bonus objectives, assuming you have flying. Its fairly quick and actually quite an enjoyable experience.

Once you hit 108 you're out of rares and bonus objectives except for Suramar which is useless for leveling. For whatever reason the rare elite mobs give you like 27 exp. The last two levels are just painstakingly slow. Legion invasions help a bit so try to hit those if they are up, once I hit 108 I ended up just not playing unless a legion invasion was up, not a fun couple of levels to get through.