Raiden isnt about staggering but rather playing solid and protecting yourself with stormcell.
If you use the double low string to advance, but teach yourself how to confirm into stormcell on block + kameo protection, youll get people to respect the low and theyll slow down with their approach. This should allow you to close the distance a little bit better to use it, but overall I feel that Raiden doesn't stagger, he doesnt do OKI, he's all about chip and making your smallest mistake really hurt.