Hmm... I think you're being a bit too negative about Siegfried.
If people are impacting B4, use it on wakeup, or play with last frame/just frame speed variation...
if your opponent just won't stop guarding, just play safely... stuff like SRSH A+B is good, like you said.
I chose Siegfried as my "spacing" character, and I use him as such. I personally think this is where his strength lies, not in pure aggression but more of a roundabout way.
You space properly with long-range moves, and you chip away at the soul gauge. again, if you're spacing properly, these moves should be hardly punishable if at all.
Should the opponent come in close range, you have tools for that (3B, throws, 6A, etc., etc.) It's better though to stop them before they get in close at tiprange (B6, 11B, agA, wrB, etc., etc.)
You never actively rush into close range unless you're advancing on wakeup or tripping your opponent up by doing it unexpectedly... all their blocking and your "offensive turtling" hurts their soul gauge and keeps you out of reach.
Now, assuming that you control when you let the opponent in or not, it should be easier to hit counterhits if you know when they're coming in, and the frames on your own moves... I believe it's more of a battle of attrition, where if your opponent can't keep up, he makes mistakes and also then leaves himself open to counterhits.
That's the theory, anyway... I'm no Siegfried expert, but this is what I thought was expected, looking at how he doesn't have the same tools as other characters.