Hi there, I don't know about Mage and Paladin but your information is incorrect about the Ranger. We cannot charge forever. In the video below, I did not let go off of the key at all and the game fire it for me. So there is a limit of how long it can be held after it is fully charge.
However, you are right that Ranger are potato now
See the video here:
I don't think that ability was Snipe. Snipe will charge up to three times and can be maintained in such a fashion that cannot be countered-played to an extent. I don't have a video to show but one of my non stance ability allows me to block for 2-3 seconds after that, it releases and all the ranger has to do is hold it till the block goes on a 35 second cooldown even though I saw the ranger's animation for snipe and tried to counter their snipe with my block but they just held it till my ability went down. That ability hits hard, like 6k damage and I tried to block it knowing that but to no avail.