The Coincounter change is yet another sign that the designers are kind of hopeless...

There are many other bosses with invisible AoE, even at lower level (Chimera), and Coincounter isn't the most dangerous thing in Aurum Val. So the change feels kind of random.

But that's not even the most important. The problem is the (probable) reason for the change. If they were really worried about helping newbies, some unimportant change to some bosses solves nothing. What they'd really need to do is to work on a coherent progression through the whole game, instead of constantly dumbing down every "older" content.