Yes, as also zephyr1 writes, there is for sure a 20% attack bonus irrelevant of troops. I am not sure of the defense bonus but apparently tha is the same. I could not find anything official on it but there is another good description here: [Primer] Defense AI Cheats or why computer gets first move, trickle mana & bonus damage and how to exploit/ defend against it for more trophies
In raid defense, the A.I. ( computer ) gets 20% a bonus damage buff, a trickle of mana per turn in addition to mana per player match, and always attacks first after the board matching is finished. This is done because the AI is very limited, unlike players that can use tactics & strategy. In fact, these advantages are always constant so you can plan for them when setting up your raid attack, raid defense teams and choosing matches on the board.
20% bonus damage buff
Players can increase damage by making matches of a color strong against the defending hero. Since the A.I. Cannot, they get a flat 20% bonus ( which is roughly the bonus of a rainbow team against a single color boss due to strong matches versus a team of all neutral colors fighting the same boss ).
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