I am kind of new to this DBAL D2.  The laser cover has already broken, and from what I have gathered this is somewhat common.  How critical is it to keep these covered?  Are they that fragile, or are the covers kind of like scope caps?  Lots of nerds using them but not really necessary.

Is there a more robust replacement?

Laser has the potential to cause eye damage if it sweeps an eyeball, so that would be my main concern.  
*Accidentally leave the invisible laser on, go to put the rifle upright in the safe, end up with a dark spot in your left eye's vision for the rest of your life.*

That being said, it's attached to your gun, so theoretically it's never pointed at anything you don't want to destroy, so shouldn't be too much of a concern.

The laser cap should have a neutral density filter function for use with the IR pointer.  It’s used to tame the IR pointer down for close range use.  Without it, the laser will be fairly bright and have a lot of splash/bloom at close ranges, even at the “civvy” .7mW level.

You can also tame the splash/bloom down with a hefty dose of IR illumination, just up to you and how you intend to use it.

It also provides some level of protection for the visible and IR pointer lenses, but given how the D2 is built with those lenses recessed into the body with a fairly deep “lip” surrounding them, it would have to be a fairly lucky impact to really damage them.  So long as you’re not doing too much UTM/sims or airsoft training, I wouldn’t really worry about the lens protection aspect.

Thanks, I'm not using it indoors and I'm not getting airsofting.  I'll put them on my scope cover shelf

I'll keep that in mind, is there a best practice to leave it on vis laser or something?

Just set it to “OFF” and you’ll be good.

I like to ensure all of my lights and lasers are off before turning off my pvs14 and removing the battery from it.  My little routine

It’s been a while since I used any DBAL models, but if I remember correctly, they’ll drain batteries fairly quickly with the selector switch anywhere but “off” (like PEQ-15s).

So yeah, just store it switched to “off.”  If you’re concerned about batteries popping/leaking, remove the battery before storage, which would avoid the problem altogether.