Also, this isn't damage, this is loss of life. This is a well designed but narrow card, similar to Ankh of mishra or cursed totem. Not unplayable, not great, but a tool you can keep around in case you need it.
It's application to accelerate decks like elves in legacy is also interesting.
The card defiantly still has its flaws, and no it doesn't directly beat bridge, but it works around it in narrow situations.
Before ballista and this card, it was almost impossible to deal with bridge, now there are lines.
As designed, the fact that it triggers on your turn and not on the end of your opponents is an interesting problem. Tapping out your team in a standoff is not appealing. On the positive, you may prevent your opponent from taking an additional turn.
I don't think this card is good enough for vintage, but I play MUD in legacy and modern where this card is more appealing. I plan on getting a Foil copy and keeping it in my collection for certain metas.
I don't think this card is must play or even a good card, I think it's niche and fringe but good in certain environments.
This card feels far too narrow and win-more to me. Already have enough creatures in play that this deals substantial damage each turn? Then you are already winning and are probably better off playing a lock piece. Few creatures in play? Then this card does nothing and you'd much rather spend two mana on a Ravager, etc.
I think the most exciting applications are as a combo piece in some kind of token or elves deck; that still sounds very fringe, though. If only it read, "whenever one of your creatures becomes tapped, opponents lose one life..."