1) They could've been partners. Fairly common to find a couple that goes into roulettes and buffs each other. Seen it happen more so with a dancer/tank or dancer/healer lately though, kinda sucks when you're playing a dps class and get stuck with these 2, but it is what it is.

2) The Astro was just being lazy. Typically in dungeons you're only ever targeting the tank and mobs if you plan to dps, so out of laziness they'd just throw cards on the one thing they've been targeting the entire time.

3) They have no idea what the cards even do other then give a damage bonus. I'd almost say the majority of people in game don't read patch notes for other classes and more often than not their own class half the time. Which I can understand, you don't play it often enough, so what's the big deal? Still with major class changes all around this expansion you'd think they'd do a little research.

4) A mix of all of the above, they're partnered, they only target the tank, and to hell with what the cards do, they help my tank buddy!