Are Rogues allergic to skulls?

Blanket statement, this is far from universally true, just a thing I've seen that is fairly common.

When I tank I mark skull so that the mob will die first. It is the lowest effort means of directing a group. In most cases skull dies so quickly I don't even have to actually tank it because after the initial maul it will get blatted from existence before doing any damage. This allows me to gather the rest of the mobs for the aoe damage and allows me to receive the vast majority of incoming damage.

Then my yellow DPS opens up on X or just whatever they feel like. They won't die from it, they will effectively kill that mob before they die. But now the skull I wouldn't have to manage, now does need management because its not getting alpha'd. And our healer is using more mana because the rogue is now taking damage from a target I didn't even need them to attack.

I don't get mad when when my mage opens with blizzard I trust them and will assist. I don't care when my DPS warrior or rogue blasts their target, that's what they're there for. But of all the things I want, just kill the skull and so often they can't even manage that. And I just don't understand why.

Edit: Thank you for the replies I figured it might be something like that. I still think that even if it increases their personal DPS, it make the overall process of clearing dungeons worse since it increase the uptime of full packs which deal less damage if you lower their number early. (Also decreases the number of targets the healer has to focus which increases their uptime as well)