So for anyone who couldnt/wouldnt/didnt follow the link, yes there are skippable dungeons along the way. Most of them are at the cap levels(50, 60, 70), but each release of the game has at least one in the "leveling" range.
Optional Leveling Dungeons:
Halatali(lvl 20) - Unlocks in Vesper Bay
Sunken Temple of Qarn(lvl 35) - Unlocks in Vesper Bay
Cutters Cry(lvl 38) - Unlocks in Ul Dah
Dzamael Darkhold(lvl 44) - Unlocks in CCH(your grand company will also offer to unlock this as you seek higher ranks)
Aurum Vale(lvl 47) - Unlocks in Vesper Bay(your grand company will also offer to unlock this as you seek higher ranks)
The Dusk Vigil(lvl 51) - Unlocks in CWH
Shisui of the Violet Tides(lvl 63) - Unlocks in Ruby Sea

As for the cap dungeons, most of them are optional. The story sends you through a few(4 at 50, 5 at 60, 4 at 70 - these numbers include "story ending" dungeons and "patch line" dungeons), but the bulk of them are unlocked via short side quests(15 at 50, 8 at 60, 6 at 70). Most(all?) of the level 50 optional dungeons are unlocked in Revenants Toll. The level 60 optional dungeon unlock quests are all over the place(some in Idyllshire, some in Limsa/Gridania/Ishgard, some in the zone the dungeon is found in). The level 70 optionals are split between Rhalgrs Reach, Kugane, and the Ruby Sea(the ones involved in the Four Lords storyline).