Combat Mechanics

So I have been working on an RTS type board game and just recently it went through a huge transformation. Instead of a an actual board with a grid allowing unit shaped pieces to be able to be moved on it, I have made it sort of like a deck building game. Although, instead of building your deck by getting more cards, you actually have to build buildings to be able to use certain things on the cards.

Anyways, the one area that has given me issues is how to make a fun unit to unit interaction without it being boring and to much to calculate.

At right now the "field" is where you will put the five buildings: the HQ, Barracks, Supply, Lab, and Research. These will have Integrity points that act similar to HP points except each Integrity point will have 8 HP. The way you destroy a building is by creating a "group" or "squad" that has more attack points than 8 HP until it has no more Integrity points.

These buildings are set in front of you horizontally where you will put cards in each "territory" or on the field which is between the players' buildings. Now, you can stack cards up to three and you can group horizontally up to three. Groups are what you attack with. Each card has an attack, hit points, and defense. Using attack you position the card facing upright, using the defense you position the card side ways. Attack subtracts HP, defense subracts attack. Whoevers HP is higher wins the battle and keeps their cards in that group. The one who loses during the battle puts their group in their defeated pile, where the cards cannot be used again. Do note there are abilities that can be enable with Lab points.

To me it doesn't seem like it would be fast and fun.

If I didn't explain it well enough I can hop on my computer and do a more in depth analysis but let me know your ideas.