I manage a machine that has an AST2500 (competitor to iDRAC in smaller vendors like Gigabyte, it rocks), and I didn't notice latency, so it's probably under 200ms.
>>tinco+(OP)
Most iDRAC type products actually use that same Aspeed ASTxxxx with vendor firmwares. If a server reports "Matrox G200e" as display adapter it's it.