As long as the connectivity and the functionality of the circuit is not compromised, I think you can connect rings with ESD ground. Infact, it will now have more surface area of large discharge.
if u hav a noisy block and want to prevent it to effect other block, better split it.
if your block's gnd impedance much lower than guard ring, then guard ring will be useless but this normally not the case.
if your chip has enough pads, split-it is the ideal case. But normally this is the constraint due to the cost.
If there is any noise block, you should use back to back diode to connect each block.
If noise level is higher than one diode turn-on vtg, use more series diode.