If going for fragments via classica dungeoneering, it will take an exceedingly long period of time, to the tune of 100s of floors that need to be completed. I heard doing elite dungeons is a good method, but i have no idea whether killing trash mobs or mini-bosses should be prioritized.
Hey there, I believe that you receive fragments in regular Dungeoneering each time you complete a dungeon. In Elite Dungeons you will receive fragments at exp drops (like killing a mob or completing a part of the dungeon) after certain time intervals. Iím not sure which method is faster, but it would probably be best to just try to level up to 120 as fast as possible (if not already 120) so that you will receive fragments at triple the rate.