No, in modern it will be totally different, because there are more human players and I can turn the bots off for more fun. Which I'm currently doing, I'm not playing against bots in modern at all, turned that off. I'd adjust the difficulty though, working on better combinations.

I'm guessing here, and I hope I'm not trying to re-invent the wheel, but bots usually copy the data they get from other players, from matches all throughout SPL, the winning teams. They try to get the best combination with the cards available. So, the fun would be in the combination of cards that the bots can play. Not frontier summoners, but something balanced. For example, in Gold Tier it could be:

all common summoners available for the bot to play
all rare summoners available
(we don't have epic summoners in the moment I believe)
50% legendary summoners available, different for each bot, maybe randomized

Same for the monsters. All common, all rare, 75% of the epics, 50% of the legends, also randomized. With that set, the bot builds the best team possible based on the data they have.

That way, the bots won't be overpowered, but it would still be interesting to play them as they will always choose the best team possible. It could also be divided still in Gold 1, 2, 3, with the bots getting more and better cards in each.

For example:

Gold 1: 100% common, 75% rare, 50% epic, 25% Legends available for the bot to play
Gold 2: 100/100/75/50
Gold 3: 100/100/100/75

This way, even in Bronze it would be challenging to play in the third Tier. Players won't need the cards at high level, but they need a wide range of cards or the best cards. When they then decide to step up to Silver, they'd have the same. Also, it would still be possible to play a great and broad Bronze deck in Silver - but you probably won't get higher than Tier 2. And so on.