Well, I've experienced similar issues. But I drink a ton of coffee which tends to clear the palette - but I notice the flavor drop when I'm not sucking down caffeine by the gallon. The iStick will give you a far better range of wattage/voltage settings than an Evod battery though - I've found higher wattages bring out all kinds of great flavor. BVC coils in Nautilus can handle higher settings too, which is great. You might burn up coils and juice faster though, with the higher power. Try out some higher wattage when you get it and see if that helps with your flavors.
DIY is interesting to me too, but I'm mostly into the idea because it's super cheap and obviously completely customizable. But, I'm leery about spending a bunch more to get enough DIY gear to get started, right after spending a bunch just getting some batteries and clearomizers and coils to get into vaping on something more than a cigalike.