I don't really think the NFL comparison is particularly relevant. The NFL system is very different from what we have in the NHL.
But in regards to nabbing players from a 'deep team' like the Hawks...sure, but my complaint is that Gillis still hasn't managed to make the CANUCKS into the sort of deep team where other organizations are eyeing up our waiver fodder in anticipation. Gillis is essentially letting other (deeper, better) organizations decide which sort of players might be available for our roster. It's begging for table scraps, and that's pretty poor considering how long Gillis has been here to develop our 'depth'.
Its a different system but i'm just using that as another example (a bit more extreme) of how a player on the waiver doesn't actually mean they can't play... regardless of sport (even basketball will have the odd waiver-wire/cut/summer league player that ends up contributing/getting into a team's rotation).
As far as developing depth goes, sometime the problem with that is the city we live in. Vancouver is a great city to live in but its also a 1 sport city with a lot of pressure on the NHL team... aka we haven't been "sellers" for years (pretty much since MG took over) and for the most part, before MG took over, we were constant buyers too under BB/DN era. When you're not a seller for all these years, you're not going to be able to hoard nearly as many picks as teams like Chicago (who seem to sell after each cup win and built their core from losing and also back then hoarding picks).
Honestly i said it before and i'll say it again... there's almost no chance MG will survive a rebuild here unless he wins a cup first so as far as depth goes, his only way of getting depth is via UFA signing (and he did make a few), waiver/trade (and with the trade route, likely giving up draft picks), or hoping his limited draft picks develop (and a couple have showed signs/promise). Honestly out of all the recent GMs we had, MG might have been the best in terms of developing/drafting/signing players and continue to ice a very competitive team because of this. His only weakness seems to be his inability to make big deals work (as more often than not, they seem to backfire, aka Ballard, Booth, etc and i have a feeling it'll extend from Florida to NJD).