In all honesty, the tax authorities do not need to be located in such a prime plot of land. That said, the level of convenience and ecosystem that is now here, is very pleasant to be around.
Office is safe, there are great dining options, and the few ancillary services located here are all very lovely to be had. Especially so with the post office, that's like extremely convenient. Beyond that, to be honest, IRAS doesn't need to be on such a large plot around Novena.