2.5 ohm @ 5.5 watts = 3.7 volts, your assuming your ohms are rock solid..they aren't, they will fluctuate .1+-.1 therefore giving you the sweet spot sometimes on 5.5 watts. I see your point though and this is when you switch over to VV mode, personally I like VW because I get a similar vape on different toppers at different ohms without needing to break out an ohm calculator. Meaning I put a 3 ohm carto @ 8 watts and get nice vapor and flavor, throw on a ProTank with 1.8 ohm resistance @ 8 watts and I get a similar vape without frying my wick. You simply can't do this on VV, it's just less fiddling...not in anyway is VW better than VV. In fact VV is better in that you can better dial in your flavor.
The same goes for VV, the ohm load changes a bit and so does the voltage.
Since you like 8 watts, use the rule of 2 on your VV gear. Take the resistance and add 2 to get your voltage, this will keep you right at 8 watts until you get above 4.5 ohm coils.
As for me, I've played with VW, I still want to build something, not sure if I want the Nivel chip or the soon to be DNA-30, but I have skills and access to a lot of equipment most don't, and I have nothing but time! But a VW Provari, nah! Besides, what would we have to argue about if they did do that?