urm depends.. that's why good to have 3 types of high rank great heroes. For me I started off focusing on Iron Patriot, Capt America with uniform and Spiderman. After that switched out Cap America with Venom Secret Wars. These 3 helped me solo those tough missions la.. based on what type of enemies are in a story mission I will choose either one to clear them .. e.g. if the boss is speed type, I'll use combat type to clear.. harder levels if it's mix of green and blue sometimes have to careful.. bring 2 strong red and green type hero in case low health attacked by the opposite type.
np.. gonna finish faster and faster since all the packages are below market price 
everyone keep asking this when they join this forum.. i think it's time I update the first page liao... which are top tier, 2nd tier, and 3rd tier heroes. 
yea hitz, check your mailbox, 3rd tab (gift section).. scroll all the way down.. the 1100 crystals should be somewhere there.
it's on every 11am the sales will start.. all packages below market price. first come first serve as all of them got limited numbers (6 to 10k quantities only). Costs 1k+ crystals for each.