MHO is - multiblock machines should be more efficient than single block. So wiki should be changed, not code.
PS I'm still using array of HP Coal Boilers and HP Lava Boilers (they built long before GT5U was created) and need good reason to replace them by multiblock boilers
Same for HeatExchanger/Turbines. Still using IC variant.
Wait till I finish implementing pollution, that'll learn ya to upgrade quick :p
That said...
I'm with Sapient on this one. There's not much reason to invest in huge, expensive machines if they're not going to offer a clear advantage. Progression balance is key!
This is my opinion in a nutshell, but I still want to hear what Blood Asp has to say.
Also I'd really appreciate it if someone can independently confirm my numbers.