Yes, mounts from chests are extremely rare. No, the mount drop rates should not be increased—not for this event, nor for any future events.
A plain 80% speed mount sells on average for 150k and sometimes even as low as 100k. A 100% speed mount (with 50% camo) can fetch somewhere around 20 million.
+20% speed = +20 million? I don't think so. The rarity of top tier chest mounts explains why they have exorbitantly high values.
Similarly, connacht sets, black/white pirate/smuggler fashion, brooms of doom, divine brooms, golden camo charms, ruby skull charms, etc are also very expensive mainly because they are so rare.
Rare items like these, as well as top tier chest mounts, should not be made common. This is not an issue of practicality; plain 80% mounts (and now even 90% witch mounts) have become much more affordable for people with a need for speed. This is an issue of preserving the rarity and worth of collector/vanity items—stuff that exists purely for convenience and bragging rights.
Why are the lower tier Nightwing mounts missing? Honestly this is outrageous, considering how many chests have been opened and only 1 nightwing mount has been seen in Gwydion. I've spent all my fortune on these hoping for at least a common one.
Something is fishy regarding these chests. Maybe OTM knew people would buy these chests solely for the nightwing mount as it was something new, and drastically lowered their rate.