In my personal opinion and experience, it's not the alcohol that's intensifying your high, it's your high intensifying the effects that alcohol has on you.
I've had a lot of experience with this, I'm a heavy drinker and I smoke all day, daily. My drinking habit started a few years ago when my girl stopped smoking with me after she smoked some prescriptions with me (Golden Goat, it was insane). She took one hit and lost her mind, hyperventilating, crying, scared as fuck thought she was dying. She completely stopped smoking and so we started drinking at nights. It started out that I'd smoke before we drank and then after I'd feel pretty drunk, I'd smoke a bowl and I'd be fucked up for the rest of the night. It's take my drunkeness to a whole new level. And when I smoked, I'd be done drinking for the night and fall asleep wasted.
As far as the side effects go, I've only gotten the drunken smoking spins when I was a kid in high school. Some of the worst spins I've ever had. Anyways, that shit don't happen anymore and never really did since high school. But I've got a very high tolerance to both weed and alcohol, been smoking all day, everyday for years and years. I've been heavy drinking for about 2 years now.
But I will say, when I'm gettin low on alch or I've got a good buzz Rollin, I'll smoke some and it gets me to a good place.
My 2 cents.