I would not do that. You still need all three. I do like the power of sending an all distance attack with the proper guards duringa kill event. It is very effective. You need other as well depending on what they have. Inf is a good Calv killer and Calv kills distance.
I also like using Calv when killing Threats. They are very fast and help you kill them all very quickly. I can beat all lot of other users to the Threats this way.
While you do not need different level of troops like you did in the past, it is important to still have all three. Each type will enable different buffs that will help in different situations.
That being said, I would concentrate on the guards, gears and such that deal with the distance troops first. They will give you a good bang for the effort. Then focus on troop buffs. Finally work on the other two.
I would not dismantle anything. They are all important.
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