I never liked passing up content and getting run through places. The numerical experience wasn't worth the loss in personal/gameplay experience.
If you got run through or skipped SM, you missed out on what to do with multiple mobs that are near your level that run. Learning how to handle that helps in BRD.
If you miss out on the princess in Maraudon, you miss out on what to do to an immune mob (immune to nature). Guess what, it shows up again in ST (final dragon).
If you skip Ramps, you miss out what to do about multiple mobs that are pretty mean if you are near their level. At least that was the experience for me. DM/Scholo was cake, but Ramps was mean unless you had Outlands quest gear. Then again, when you realise you needed better gear, you did quests to get it and you got exp and learned how to do the quests so they became easy. Both things helped. You became better at dealing with things that will help you later.

The idea for me is do most things (except very necessary collection quests) because it helps you learn what to do for later. Having a high level char that has done it isn't the same as having your group do it (unless you outlevel it). Things that I noticed: hunters/lock pets walk beside you so they are closer to the mob, so you have to walk slightly farther away so you don't aggro them; getting some tanking gear for my DKs helped when in instances and using Outfitter to change gear--If I hadn't got the other set, I wouldn't have noticed how much Outfitter really helps, doing PVP on my hunters made me realize the helpfulness of round-robin on a single macro (freezing traps) and inside a longer macro (concussive mixed with DPS)---I never would have used concussive and traps outside of PVP, so I never would have learned what to do with super hard mobs insisde instances (traps).

Again, to me, do most things, they will help you for later. Think of it as a learning experience more than a grind. If things are too easy, you are in too low of a place. Hope that helps and good luck.