Try Rogue-Bot. Start off with Launch Grenade and aim for Morph Ball. Then go for Launch Net, but don't bother investing the second point. Rockets come in handy once you hit the lower levels. Improved logic is also a must when you can spare the point.

Try to save energy potions to boost your maximum energy once you've got Morph Ball. Trust me, you won't need them as much as you might think.

Basically Rogue-Bot is a ranged character and you'll want to stay out of melee as much as possible given that you have very limited ways of regaining health. Just be careful not to blow yourself up, morph and run when low on energy.

I just got combo mode recently. No clue as to why I didn't bother before. I like it. It is definitely a different type of game. I managed to save up for one of the scrolls. And am currently trying for more. I like the Mystic for combo becuase of her fiery imprisonment ability. That along with her distance attack makes it easy to pick off bad guys and keep your combo rate high. So far I've had it up to about 8.0 but would love to get it much higher. The points definitely start to stack up when you do.

The bandit levels work well for supplying your Rogue. If you can 10-15,000 points per level you can spend enough to get what you need and have some left over to build up for later on. By the time you get to hell I found it was pretty easy to get the 160,000 points needed. Whether or not I could get double or even triple that to get all the scrolls depends on your patience. There is a bit of grinding needed I found to make this really work. Nice to have the added boosts to the regular games though. :)