Find Wisp Essence

As your companions begin to approve of your decisions the outside of the tarot card turns from black to white. If you're romancing a NPC and you go on a personal quest, after completion the face of the card will change based on the decisions in the quest. I've found it difficult to gain full approval from all companions in one playthrough. It's not the same as DA2 due to the fact that if you get full approval from one character and no longer appears on the screen "Iron Bull Approves" if you choose something he disapproves his approval will go down again and not stay at full approval.

Try to hang back a bit while your tank (or other characters) start attacking, so they grab the enemy's attention (aggro). Your warrior tank should have abilities like Challenge and War Cry - that'll definitely get their attention off you.

I'm playing a mage myself. When attacking a rift, I switch to my warrior or any of the other characters and simply use them to launch the first few attacks. Then switch back, and you shouldn't have aggro.

Like someone noted in the comments - it does seem that enemies who are currently not attacking you, but have not been aggroed by anyone (e.g. not attacked, or taunted), will shift their focus to you once you start disrupting. The only way to solve this is by focusing it down, or by taunting it with your tank.

Also, I've noticed that, when using a different party member, the option to Disrupt Rift also appears - but I haven't actually tried that, so I don't know what happens.