Incense still sucks
Today I use the free incense from the Mew quest.
In 30 minutes I was averaging around 1 pokemon every 5 minutes while sitting in front of my computer.
Niantic should buff incense. I also think nanab berry needs a buff.
Answers
That's not a very good analysis - in rural areas you don't get spawns that often and inciense is pretty good if you go for a walk. It also helps if you travel by bus in an urban area, combined with Go+ or the "skip animation" exploit (or both). You can grind a lot of stardust in just 30 minutes, and I can't think of any physical way how to catch more with a buffed Inciense.
Yes you will but data has already been done and proven 1 incense used the right way =30 mons= 5,000XP min with great throws and a min 3000 dust. Thats on top of what you would catch normally. If you still believe its not worth it despite multiple trials and many people complying data, then just toss them since there worthless to ya.
Incense is ideal when you are in a location with low spawn rates. I was on vacation last summer in a location that had no gyms or stops close to where I was staying but thanks to incense I caught my only Corsola.
I think the best enhancement for lures and incense would be to have them spawn CP and/or IV boosted mon.
Granted that even you could be sitting still, with no pokestops around, and possibly without a spawn point (or possibly even no local biome at all), one pokemon every 5 minutes guaranteed starts sounding pretty notable.
Especially good if you want to keep you're streak going and you're in the middle of nowhere or temporarily immobile (popping one 15min before midnight will ensure a spawn for two day's worth of the streak).
Incense it also useful to increase spawn rates of pokemon that are already common in your particular location, as its spawns are based on local spawn probabilities. If you spend an hour or two at a remote spawn point, two or three more catches can make the difference between meeting your candy requirements or not. The same holds for particular times. Anecdotally, on Bulbasaur community day I did not have the time to play for longer than 1/2 hour and not in a good hunting area. The three Bulbasaurs spawned by incense made it possible for me to get one Venusaur with Frenzy Plant even so.