Meh, really not necessary in my opinion. Sure, it helps to have a close-to-level legendary in at least one slot, but you can get through with purple, blue, green - and even white rarity items that are actually at level. The trick is to do what the guide @Kurtdawg13 linked says - be strategic, use slag, don’t rush, persevere.
What I do is push through the main story up to the “go talk to Claptrap to go to Heroes pass” bit. Along the way I’ll do side quests that net me only XP, cash, eridium, or missions rewards that aren’t legendary or blue unique items. I’ll also do parts of Hammerlock (up to somewhere around “Whoops!”), all of Torgue main story, and as much of Hammerlock and Tiny Tina as needed to get me to level 72 with maximum storage. Then I’ll wrap up main story so all the remaining quests level to 72. At that point, you can farm for whatever you like, and decide if you want to do OP levels or not.
If you already know you want to go all the way to OP8, then you may want to skip missions and side quests in the DLCs that you want to get at max level. More likely, though, is that you’ll farm the level 72 versions to get you through a few OP levels, then reset and re-farm, etc. One thing though: unless you are extremely single-minded (or have a lot of help) getting from level 52 to OP8 on the same character could become painful. Don’t be afraid to mix things up and try different characters in between rounds if you find things getting stale.