On another note; I remember reading somewhere that the V-2 was more efficient than the Luftwaffe's bombers. Why? They cost a few percent more per ton of explosives put on London, but they couldn't be intercepted, and they lost no pilots. I can't find the source right now, so I could be wrong. But if so, it would only take a few extra years of rocket development, and a slight retardation of nuclear development, to see a Second World War style conflict typified by thousands of rockets landing on enemy cities, rather than the bombers we saw OTL.
You can probably find statistics to support any position, although I'll note in Speer's book he says the V-2 was a waste of time.
But there are simple reasons why V2s don't add up:-
1. Warhead amount:
A V2 delivers a 1 ton warhead.
A Lancaster, B-17, B-24, B-29 etc. delivers between 2 tons (long range mission on a B-17) to 6 tons (Lancaster) to 9 tons (B-29), or more
So to match a single 1000 bomber raid, you'd need say 6000 V2s (more than the total amount Germany was able to produce, let alone launch, during the entire war).
Now to match a month of 1,000 bomber raids, you'd need inconceivable numbers of V2s
2. Warhead delivery:
V2s explode on impact leaving a crater, and are only suitable for carrying certain types of warhead. Maybe this type of problem may be solved with another V2-like delivery system, dunno, but it's an issue.
3. Warhead accuracy:
Accuracy of V2s compared to bomber averages is terrible. Remember V2 accuracy is uniform, but bomber averages vary by weather, so even a poor average can include some relatively pinpoint bombing.
Also improving accuracy of rockets is pretty much certain to be harder than improving accuracy of bombers.
4. Range
V2 is limited to 200 miles.
Now moving on to other types of conventional ICBMs.... payload ratio and accuracy is going to get worse as you increase range and add more stages so points 1 & 3 become even more significant against rockets.