For the most part you'll find the best guides in YouTube, just type the name of the dungeon + guide or tutorial and you'll get a ton of results. Some lvl. 50+ dungeons changed since its release so pay attention to the date of the guide and try to look for newer guides.

Having said that for a young Gladiator looking to be a great Paladin gdoggcasey guides are the best I've found:

gdoggcasey's Tanking Guide for Beginner Gladiators