You'd have to build the D30 with 30 spline chromo shafts and chromo axle joints, and you'd have to build the D44 with chromo axles and chromo axle joints. Since the D30 would have unit bearings and 30 spline stubs, and the D44 would have lockouts and 19 spline stubs, as far as axles go the D30 would be slightly stronger. But, the D30 weak point would be the ring and pinion and the housing, and you're still going to spend some coin on it making it all 30 spline.
If you don't do rocks, only dirt and mud, and you're a careful driver.......who knows. Personally, I'd hate to spend that kind of money on a D30 when you already know you're going to run big tires. Yes, the D44 is a lot of work, since you have to build mounts, but you'd have to truss and reinforce the D30 as well for it to have a chance of living so that's a lot of work also.
As far as getting axles to live with 37's, yes, it all has to do with driving, type of terrain, and good or bad luck. I only broke my D30 with 35's one time, a Spicer axle joint. The D44 in there now with 37's has broken too many times to count.......between me and the new owner. The list includes multiple locking hubs, multiple stub shafts, spindles, CTM joints, and an inner axle shaft.......everything is chromo. So, yes, some say they are making a D30 live on 37's.........but what are they doing?
I have one friend with a TJ with a 30 spline D30 on 37's, no front breakage and he tells me he wheels the hell out of it. Yet, when I look underneath it there isn't any rock rash, so where does he go? I can't invite him to go with us, because I know he wouldn't last a 1/4 of the trail. It's all relative........