Safest block strings, pretty sure back 3, 2 is safe on hit, but it's easy to interrupt, and the second hit isn't guaranteed on block so watch out for someone throwing armor/x-ray in there. Back 1,2,2 isn't safe, but you can cut it short to just back 1,2 which makes it safe, 1,1,4 is probably safe, although I usually just poke with the 1,1 part. Also it's not a string, but I use standing 4 gunshot held pretty much to start all my dash offense, at the right spacing it sets you up for either a very hard to anti-air jump or a gunshot to deter retaliation or a dash to throw. Also don't overlook his sweep, it's really good, same with his uppercut. When it comes to interrupting predictable strings/making space his uppercut is almost as good as down + 1 so long as you are sure it won't whiff.
Well Stryker is weird in that I don't suggest doing his optimal damage combos, especially offline. Basically I use, back 1,2,2 nj 2 dash 1,2, gunshot then I usually do the reset with standing 3 to gunshot. I like this combo because it's reliable and it frontloads the damage, so even if they breaker it at the NJ 2 you still get around 20%. You can make it longer with meter by doing 1,2 bang bang then another 1,2 gunshot, but it's not really worth the damage unless it'll get you the round. Also sometimes it's worth dropping the 1,2 gunshot to just reset them off the launch as a mind fuck.
Off back 3, 2 I like to do dash uppercut (Thanks CRKFIEND) but if you're nearing the corner and worried they might pop out you can do dash standing 4. Also you can extend this one a lot by using dash 1, bang bang and then dash uppercut or dash 1, rolltoss. In fact if for any reason you want to switch sides with your opponent remember that you can end either combo with 1, rolltoss instead of uppercut/reset.