I just don't think we'd be doing Sami any good by putting him in even more favorable situations. In my opinion, you need to be willing to use the kids outside their comfort zones at times(within reason... otherwise you're just going to cause the kids to flounder), because at some point the opposing teams are going to do whatever they can to do it for you, and you want your kids to be ready for it. That's exactly what happened to Leddy in the playoffs, and it's why it's not as common to see sheltered offensive defensemen like that.
I think this happened last season already:
In these 20 games Vatanen had ZS% of 50 or less:
Sun, Oct, 13, 2013 Senators 1 at Ducks 4
Wed, Oct, 16, 2013 Flames 2 at Ducks 3
Fri, Oct, 25, 2013 Ducks 2 at Senators 1
Thu, Oct, 31, 2013 Ducks 2 at Bruins 3 (SO)
Sat, Nov, 2, 2013 Ducks 6 at Sabres 3
Fri, Nov, 29, 2013 Flames 2 at Ducks 5
Tue, Dec, 3, 2013 Kings 3 at Ducks 2 (SO)
Sun, Dec, 15, 2013 Oilers 2 at Ducks 3
Sat, Dec, 28, 2013 Coyotes 2 at Ducks 3 (OT)
Tue, Dec, 31, 2013 Sharks 3 at Ducks 6
Tue, Jan, 7, 2014 Bruins 2 at Ducks 5
Fri, Jan, 17, 2014 Ducks 2 at Blackhawks 4
Mon, Feb, 3, 2014 Blue Jackets 4 at Ducks 2
Wed, Feb, 5, 2014 Blackhawks 2 at Ducks 0
Sun, Mar, 23, 2014 Panthers 2 at Ducks 6
Fri, Mar, 28, 2014 Ducks 3 at Oilers 4 (OT)
Sat, Mar, 29, 2014 Ducks 5 at Canucks 1
Mon, Mar, 31, 2014 Jets 4 at Ducks 5 (OT)
Sun, Apr, 6, 2014 Ducks 2 at Oilers 4
Sun, Apr, 13, 2014 Avalanche 2 at Ducks 3 (OT)
In these games he had a CF% of 53.4%, average ZS% of 39.34 (Didn't find number of zone starts so this is an average over the game by game ZS% stats provided by extraskater), and while he had a low QoC, 27.5 in these games, there was a game like the March 28th against the Oilers where he had 22 minutes of even strength TOI (26 minutes total) with QoC of 29.5. In that game he was the least sheltered of all D-men (with Beauchemin), had the highest QoC and team lowest OZS% with Getzlaf (a high QoT, though, indicating that he might have played a lot behind Getzlaf's line). Fowler was out that game, Lindholm, Sbisa, Lovejoy and Robidas split the remaining TOI giving them all TOI around 17 minutes.
It seems to me that Vatanen isn't too much in trouble when he isn't sheltered though I admit the sample is too small for the CF numbers to be reliable, that's why I didn't even list the GF% of this span (though it would have been flattering to Vatanen) as goal stats are much more noisy than corsi.
It also seems like Vatanen was an option to take on the big minutes when Fowler wasn't in the line up even if it was just one game late in the season without any fear of missing the playoffs. Or maybe it was exactly as you put it, using him outside his comfort zone, within reason.