Warriors, I need your help.

[Lumadurin]

The latter half of the 50's, 60's (and soon to probably be 70's too) is when tanks and healers have the roughest time because that's the point where the highest ilvl from the last expansion (Aug. Ironworks/Shire/eventually-Scavean) falls off and you'll no longer be overgeared for dungeons.
It'll rectify itself once your ilvl goes up. Going through the MSQ you don't feel the power spike as much because the game gives you free level-appropriate HQ gear. But if you're leveling a tank after that then you'll have to play more conservatively unless you can afford to get a full crafted set every 2 levels (and also feel like wasting your gil).