Pre-max level dungeoneering should always be executed with care. You don't know the other party member skill levels only their general item level which doesn't say much. I employ a similar tactic to yours in appraising my fellow party members proficiency at various pull sizes. I throttle it back if someone is uncomfortable with the pull size ,or rev it up if people feel they can handle more. The item levels we enter dungeons at for the first time tend to be lower end of desirable so tanks are a bit squishier ,and dps is a bit slower in most cases. I have to say in Heavensward I didn't feel quite so vulnerable in the leveling dungeons , but there were some major tank modifications made so it's to be expected I suppose.