maximum eirp for ofdm

Assume an OFDM transmitter has an EIRP of 100W.
WiMax has around 256 carriers which means 100/256 Watts for each carrier
DVB-T has 2k and 8K modes so the power is 100/2k and 100/8k Watts respectively.

Now in theory the WiMax signal should be more reachable compared to DVB-T but DVB-T was designed for digital broadcast so it must be even more reachable than WiMax. My question is, why is 2k carriers the minimum choosen for DVB-T when it can do better with 1K and less with option to use 8k for very dense areas? Hope my question is clear.

Note: I am aware that WiMax uses OFDMA which is only a simple extension to OFDM.

Note that Wimax does not use *only* OFDMA. It could use also BPSK or QPSK if the OFDMA in 256QAM can't (pure and simple) be used...

OFDMA is used for the last stage modulation. QAM, QPSK etc are inner digital modulation techniques. They are not substituable.

Also, I am not sure if WiMax supports 256-QAM, the highest IIRC is 64 or 128QAM?
Correction: I just found out that 256-QAM is defined for WiMax though optional.