Electrically speaking, we're dealing with a parallel circuit--1.8Ω dual coil is really
two 3.6Ω coils side-by-side on the same connector.
1.8Ω is perfectly fine on an eGo-class battery, but a 420mAh battery won't last very long with a 1.8Ω atty. If you want to use dual coils on your eGos, get a larger capacity battery--at least 650 mAh. Or switch to single-coil atties of medium resistance--1.8-2.2 Ω. Dual coils are tricky.
1.1 or 1.0Ω is sudden death though. As soon as the resistance of the atomizer goes down to 1.0Ω, the infamous MOSFET will fail. It's a well known flaw in the design of the short circuit protection in the eGo class units.
It sounds like your atty shorted and possibly killed your battery. Do you own a multimeter? If so, check the resistance of your atty--and the voltage of your battery. That should give you some clarity.