It's a valid concern, as Red contributed a lot of veteran leadership. I think we miss the intangibles more than the on the field performance.
I don't see a change in philosophy. A few reasons why:
We have one of the most dominant defenses in recent memory. At least in the last 10 years. You don't tinker with that when it works so well.
They cut Bryant for a couple of reasons, price and amount of snaps he played/value at that price. It doesn't mean they went away from that position, or that personnel grouping.
You replace Bryant with either a cheap FA addition (which you honestly can't plan for...you can plan for a guy, say Houston from the Raiders, but you can't plan on how much he costs), or depth. We have Brooks, Williams and Scruggs. Now that Scruggs weighs over 300 lbs, he'll hold up.
Bennett played most of the snaps anyways (see the comment on value/snap). So, Bennett will still play more snaps (or at least an equal amount at that DT spot) so he won't wear down. Even if we did go lighter, we have a solid DL rotation, so lighter guys can hold up if they're not on the field all the time. Holmgren's team (specifically the 05' defense) didn't have the depth we do. We would rotate guys out, but it showed.
We've also shown an ability to locate talent at almost any level of the draft and plug it in to our defense. Bryant isn't a hard talent to replace. Guys like Bennett, Thomas, Sherman etc. are a lot harder to replace, so you cut the guy you know you can find cheaper and easier and pay the guys that are harder to replace. I'm not too worried really.