I dont think a bonus for towersis a good idea.having a legendary already makes for a big gap in survival time. But maybe it would be a good idea to give a bonus on legendary drop chance when having all golden cards in one kind of cards. A lot of people are not heading for maximum survival time because they want to wait for all legendarys because then your survival time goes up alot. So everyone is just doing daily quests
Ok, how about if you get all normal golden cards you get an increase in legendary drop rates, then when you get all golden cards you get a Legendary card that has a unique ability. If there are legendary cards on the field, you get a bonus 25% attack speed per legendary, for 8 seconds, cooldown 180?