Mordremoth's biggest weakness could also be what you're accusing Anet of. It spread too much too quickly.

You feel like it's resourceful, but it's not too different than the other dragons. It takes what it perceives as strong and copies it. It also copies miscellaneous other creatures along the way like the Itzel and Nuoch. Is this really that different from the other dragons' corruption? Zhaitan corrupted the kings of Orr into floating laser eyeballs of power. Jormag specifically targeted the Kodan's leaders seeing them as a source of power while promising power to the Norn and Grawl for woship. Aside from Primordius that just destroys shit, the other dragons are just as opportunistic. Mordremoth just got lucky and caught a few powerful specimens.

Mordremoth is a dragon of the mind, so it just feels crafty. Perhaps it was just spreading too far too quickly and was forced into this course of action. Also, Mordremoth was very lucky in the existence of the Sylvari which gave him a strategic advantage that the other Dragons could not: to attack his aggressors from within.

Kraalkattorik has much emotional baggage because of the Snaff/Glint encounter. This one will be fine.

Bubbles is a dragon of the depths. Underwater stuff and the abyssal depths tend to have some really creepy stuff in real life. Bubbles will be fine in terms of aesthetics. Add some Abaddon tie-ins, and you have the creepy factors turned up. Plus, Bubbles has the mysterious angle better than any other Dragon so far. Also, there's the mysterious Krait orb.

Primordius and Jormag are more of the forces of nature. Jormag wants to take everything while Primordius wants to destroy everything. They're also perfect for potentially pitting against one another which would would provide an epic storyline beyond punching a dragon with a laser or going into a dragon's mind and punching it there.

I think everything will be fine.