Personally, I would house rule it so that Ranger abilities, Sneak Attack, and Divine Smite also get doubled, but that is just a table rule.
For using the current UA with the rest of the 5e system, I guess that is a fair choice. But it might be worth considering the new rule as written once the entire 1D&D system is available. If this is just a single part of a system wide balance/fight swingy-ness change, then your house rule defeats that.
This really feels like a snub to optimising... Which is probably good to some extent. It can be difficult to resist the optimised builds when they provide crazy results over a built thats more for flavour. But if the difference is reduced then suddenly players can take their flavour builds without feeling like a tagalong to optimised builds one hit killing everything.
However, I also see the issue that scoring a critical hit is supposed to be an amazing moment of triumph that have the players pumping their arms in the air for victory. Although I would still argue it was more of a triumph moment for optimisers that had even more excess of dice.
If I were to homebrew for keeping the hype of the Critical hit while bringing things down and even across the builds, I'd simply triple rather than double the weapon dice.
Sneak Attack, Dred Ambusher and many other abilities to add some extra damage to attacks were all created have been built into many optimisations that stack on extra attacks, advantage and much more to send damage through the roof. Without them using Critical hit doubling, they're still acceptable abilities but not necessarily something for optimisers to drool over.
My expectation is that the new PHB will change the assassinate subclass feature into something that's a bit less potent but more consistently useful.
Even then assassinate isn't that potent as it works off the 5e surprise and initiative. If a surprised creature goes before the rogue in intiative then they are no longer surprised so assassinate won't work.
That's not how surprise works. Once initiative is rolled, the DM decides if the creatures being surprised are surprised or not, then on start of combat, surprised creatures do not get to act on their turn.
The new critical is good to avoid those 1-2 rounds boss fights, that is clear sign of imbalance. So doubling the dice should be limited to controlled things, like the weapon itself, and for magic the attack cantrips, as you cannot upcast them.
Divine smite critical is an abuse, more when you spend the slot AFTER you know that hits. In the case of spells, a level 5 inflict wounds to an immobilized target are 14d10...
In the case of rogue, I'd limit it to the Assassin, but instead of modifying the critical rule itself with an exception, simply change the assassin ability to double all damage dice for the first surprise attack. Maybe the same for Dread Ambusher and other subclasses of that kind.
But, I don't like much the idea of removing criticals from foes, as it makes combat more interesting. Some kind of middle point to preserve the combat pressure and avoid too short important fights.
For using the current UA with the rest of the 5e system, I guess that is a fair choice. But it might be worth considering the new rule as written once the entire 1D&D system is available. If this is just a single part of a system wide balance/fight swingy-ness change, then your house rule defeats that.
This really feels like a snub to optimising... Which is probably good to some extent. It can be difficult to resist the optimised builds when they provide crazy results over a built thats more for flavour. But if the difference is reduced then suddenly players can take their flavour builds without feeling like a tagalong to optimised builds one hit killing everything.
However, I also see the issue that scoring a critical hit is supposed to be an amazing moment of triumph that have the players pumping their arms in the air for victory. Although I would still argue it was more of a triumph moment for optimisers that had even more excess of dice.
If I were to homebrew for keeping the hype of the Critical hit while bringing things down and even across the builds, I'd simply triple rather than double the weapon dice.
Sneak Attack, Dred Ambusher and many other abilities to add some extra damage to attacks were all created have been built into many optimisations that stack on extra attacks, advantage and much more to send damage through the roof. Without them using Critical hit doubling, they're still acceptable abilities but not necessarily something for optimisers to drool over.
That's not how surprise works. Once initiative is rolled, the DM decides if the creatures being surprised are surprised or not, then on start of combat, surprised creatures do not get to act on their turn.
The new critical is good to avoid those 1-2 rounds boss fights, that is clear sign of imbalance. So doubling the dice should be limited to controlled things, like the weapon itself, and for magic the attack cantrips, as you cannot upcast them.
Divine smite critical is an abuse, more when you spend the slot AFTER you know that hits. In the case of spells, a level 5 inflict wounds to an immobilized target are 14d10...
In the case of rogue, I'd limit it to the Assassin, but instead of modifying the critical rule itself with an exception, simply change the assassin ability to double all damage dice for the first surprise attack. Maybe the same for Dread Ambusher and other subclasses of that kind.
But, I don't like much the idea of removing criticals from foes, as it makes combat more interesting. Some kind of middle point to preserve the combat pressure and avoid too short important fights.