instead of asking "should i weld it more?" why not ask "why shouldn't i weld it more?"
i'm taking steel fabrication and i wouldn't let that out of the shop. those are just big tacks to me. the spaces at the top and bottom where the spiders are touching the ring gears -- fill them.
find a piece of ~1/8 (more or less) in the scrap bin and cut it to fit between the spiders like cybrfire showed pics of. fill those too.
i *personally* would NOT run what you've posted.
it's like an hour of 2 of your time and maybe 20-30 bucks of welding rod. that's a good deal to never have to worry about your diff again.
like one of the other posters said -- if i welded a diff it would be a pile of weld that would just get ground down to fit in.
get out the welder and give 'er!