kill order healer archer sorcerer then melee, stick together and tank peels mobs off healer if possible

if there is no healer kill the archer, if there is no archer, kill the sorcerer and so on and all focus the one target to drop them quickly.
if there are 2 of the same mob ensure all are attacking the same one within the kill order i have been in alot of groups where people ignore the archers and attack the melee and everyone dies its not a healers job to spam a high costing big heal and go oom because groups are stupid.

In lower content it may not matter that much but when you are doing Trials and such it deffinetly does, in order to complete them you need to work as a team ensure you all know what to do and be smart i.e. if theres a big red circle on the ground get out of it, if theres an NPC building up a power shot thats visually displayed with a big build up swing and little yellow lines coming off them then block to knock them off balance.

in a game like eso where class if a formality and people have the ability to do whatever they like then protect yourself you have 2 weapon bars, equip a healing staff in the second one if your doing a trial so if a healer goes down someone can heal why dps gets them back up and dont always rely on the healer because at some point he may be out of magicka or stunned and not be able to heal you if your heath gets low pop a heal yourself if takes a second and you could save the group a wipe.

Everyone has the ability to add mitigation and defence to thier build because lets be honest whats better? A stone pillar surrounded by wet tissues or a stone wall.
Think about it people.