Since DCI carries information like # of UE's is scheduled per TTI. DCI travels over PDCCH. PDCCH occupies few OFDM symbol from the start at per subframe. So I guess if you want to increase the number per TTI then you have to increase the PDCCH resource as well as PDSCH resource.
For example: If PDCCH resources are increased to support more # of UEs per TTI but PDSCH resource is not enough to carry UE's data. So take care of both PDCCH as well as PDSCH resources.