A slightly more elegant way is to dial up the opacity on your glow using a feComponentTransfer on the alpha channel.
<filter id="label-glow">
<feFlood flood-color="white"/>
<feComposite in2="SourceGraphic" operator="in"/>
<feGaussianBlur stdDeviation="2"/>
<feComponentTransfer>
<feFuncA type="gamma" exponent=".5" amplitude="2"/>
</feComponentTransfer>
<feComposite in="SourceGraphic"/>
</filter>
You can adjust the average intensity of the white by changing amplitude and you can adjust the intensity falloff by changing exponent.