In addition to what has been said above, my two hardest on normal were Storm and Iceman. These are combinations of strategies I have seen on the net and my own personal play preferences. Here is what I did:
For Storm, use whatever costume you like as long as it has Static Charge and Defense which you can max out (used her Astonishing costume) and I used the Dark Uru Hammer for Gear. I maxed out her Lightning Stike which I used to kill everyone I could before I entered a room and then used it and melee on whatever was left. I kept whirlwind armor on for the Murder Bots in case they kamikazied me. Once you get to the bumper car rink I used the Helmet of Titannus gear in case I got acid splashed too much and bumper carred just enough to get to 20000. Once done I went after Husar with the Helmet on and whirlwind armor active and just meleed/Thunder Struck her to oblivion.
For Iceman I used the Spiky costume with Cold Mastery and Defense maxed out, Attuma's Wrath Gear, and Frigid Aura, Ice Beam, and Polar Explosion maxed out. First thing in is to activate Frigid Aura (automatic kill on the leepers if the grab onto you so keep it on at all times) and press Y twice (use the Y,Y Ice Slide everytime you move from one fight to the next to save time) to ice slide to the first Fire Giant. Steal his sword and you should have everyone from the begining of the level right behind you. Beat the Giant and the rest of creatures and then go back to the area with the statue to kill the respawned leepers and pets. Once done with them head to the beginning of the bridge. While you attack the leepers and pets, the Fire Giant should respawn and come after you. Beat them all with the sword, Ice Beam, and Polar Explosion but throw everyone but the pets and giants off of a ledge for quick kills. Kill everything as you move through the level and move onto the large ledge on the right just before you get to the final area with the pets and leepers and kill everything. Once done, move to the Fire Giant and take most of his life away before taking the sword. Do not use your sword on him to kill him so you have it a full power against Mysterio. Once the Giant is dead go through the arches, drop the sword, activate Frigid Aura, pick up the sword and prompt the boss fight. Keep Frigid Aura on and attack Mysterio with the sword moving around to his sides whenever the teleports. Once the sword is done you should have him at half health. At this point go into your Hero details and max out and assign Frost Bite and use the Spider's Bite Gear. Once back into the fight, activate Frost Bite and you can duck and move to melee Mysterio to death. I finished with 51 enemies killed and completed it in 7 minutes, 22 seconds on my first try this way. I shaved a minute and a half off my time best time using it.
If you have any questions, comments, or concerns please let me know. If you are going to leave a negative vote, please let me know why beforehand so I can fix it if it was due to a mistake.