Hey GMJ.
There is just a few "laws" you need to wrap your head around here. This basic calculator
Online Conversion - Ohm's Law Calculator will give you your answers to all of your questions here. OK, you have a nicstick, which gets hot right ? Let's say the batt is 280 milliamp and your atty is 2.5 ohm right ? Your power is measured in WATTS, right ? So... lets do math.
Plug in your 3.4 volt nicstick ( educated guess) and 2.5 ohms (atomizer educated guess) and your total power is.........
4.6 watts for your nicstick. This makes alot of sense for your overheating the atomizer.
NOW... Lets take your new RIVA 510 at 3.7 volts and a 2.2 ohm atty...your power will increase to..
6.2 WATTS That is the difference between your current nicstick and the new RIVA you have ordered.
The difference will be much greater and to your satisfaction.
Just remember...the ohms "LAW" will be your guide to your "WATTS" power hit.
This is simple stuff here my friend with this calculator. Just remember, WATTS is your POWER. (Think light bulb).
Hope this explained why your atomizer is getting overly hot.
Vape On !!
P.S. If you go with a 2.0 atty/carto, your power will increase to 6.845 WATTS and your vape will be at almost a perfect sweet 10 for your RIVA.