Currently Letho + D-bomb is not really problematic due to deck diversity and because it is inherently situational. If an opponent uses Letho in round 1 on a developed board (most common scenario), the opponent can instantly pass knowing that another card has to be played in order to achieve an actual impact (if D-bomb - two more cards if we count the D-shackles + Menno Coehoorn). As such, the move inherently grants the 'victim' card advantage, unless he plays on (not recommended, obviously).
As a finisher, the move should inherently be weaker; due to fewer units generally being present at later rounds coupled with the prevalence of agility, the effects of a Letho can be mitigated (keep track of how many golds and silvers have been played, often it is easy enough to spot a Letho deck due to the absence of one of either the staple NG silvers or golds).
That being said, from a long-term perspective Letho + D-bomb inherently limits design space. NG really cannot be given another CA tool on top of Cantarella/Ciri since it would off-set the only real (and great) weakness of the combo. Additionally, the combo is inherently extremely oppressive to certain archetypes (i.e. Queensguards/Reaver Hunter recycling decks, amongst others). In a ladder environment that is not such a big deal. In a tournament setting in which you know your opponent's leader/faction in advance, it can be gamebreaking.
Lastly, it also presents a challenge in terms of future card design. As long as Letho + D-bomb exists, cards akin to (not identical to) Queensguards, Reaver Hunters, Nekkers etc. cannot be created due to propelling Letho into an "I win"-button with no real counterplay.
I did not originally expect that they allow D-bomb to reset Letho to 1 strength. I assumed it was a bug due to the wording of the card as of previous patch. I think he should - like in closed beta - still strengthen rather than boost, making the combo into a 3-card combo (Letho + D-bomb/D-Shackles + Menno/Scorch/Igni/Villen pop). That would also expand Nilfgaard's design space further down the line, i.e. by giving them another CA spy (being the spy faction).
As a finisher, the move should inherently be weaker; due to fewer units generally being present at later rounds coupled with the prevalence of agility, the effects of a Letho can be mitigated (keep track of how many golds and silvers have been played, often it is easy enough to spot a Letho deck due to the absence of one of either the staple NG silvers or golds).
That being said, from a long-term perspective Letho + D-bomb inherently limits design space. NG really cannot be given another CA tool on top of Cantarella/Ciri since it would off-set the only real (and great) weakness of the combo. Additionally, the combo is inherently extremely oppressive to certain archetypes (i.e. Queensguards/Reaver Hunter recycling decks, amongst others). In a ladder environment that is not such a big deal. In a tournament setting in which you know your opponent's leader/faction in advance, it can be gamebreaking.
Lastly, it also presents a challenge in terms of future card design. As long as Letho + D-bomb exists, cards akin to (not identical to) Queensguards, Reaver Hunters, Nekkers etc. cannot be created due to propelling Letho into an "I win"-button with no real counterplay.
I did not originally expect that they allow D-bomb to reset Letho to 1 strength. I assumed it was a bug due to the wording of the card as of previous patch. I think he should - like in closed beta - still strengthen rather than boost, making the combo into a 3-card combo (Letho + D-bomb/D-Shackles + Menno/Scorch/Igni/Villen pop). That would also expand Nilfgaard's design space further down the line, i.e. by giving them another CA spy (being the spy faction).