All dating methods have given wild numbers many times... I think what observer is trying to communicate is we are relying on decay and amount actually injected by the sun being static from the beginning of time...that is one hell of an assumption. It seems to really just be needed conformational bias over true curiosity and science.
Even just a 1 percent change for any given amount of time in the past could effect tests by millions of years depending on when the change happened and how long. Very long term changes of extreme changes (example say a 20 percent change) could effect results by billions.
Want to see true accurate dating (as much as you can ask for) just follow the money not fluff. Look at what oil companies use, they don't give a shit about agenda, evolution or anything of the such...just money and finding oil, so it must work. Their system is accurate for around 500-1500 years...this is a system I can agree with.
I think you are forgetting that paleontology has no "agenda". No one is trying to prove evolution to you, because no scientist takes young earth creationism seriously any more. Every time a fossil is dated, no one rubs his hands and says "Yeah, that's gonna prove them YECs wrong! Wooohooo!". They just date a fossil. If there is someone with an agenda it's all the YECs desperate to disprove everything they don't like. Every time I check an article in Answers in Genesis purporting to disprove radiometric dating I look at the footnotes and it's always some "Creationist Science Institute" research published in a creationist journal.
No, radiometric dating isn't ALWAYS right and it does occasionally give wild numbers. That's because you have to know what you're doing when you're dating things and be careful not to fall in the various traps that exist. Of course real geologists know what those traps are and how to avoid them, but every time a creationist attempts to "disprove" dating methods he intentionally falls into them so that it gives him a wrong result. It's not the dating method that is wrong but the way he used it.
Saying that we don't know if the decay rates were always the same is akin to saying we don't know if Newton's laws were always right, or doubting the superposition principle. There is absolutely no reason why the decay rate should vary, and it doesn't explain why results from all dating methods fit together just fine. I don't know what you are referring to by "amount injected by the sun". I've seen many researches proving the assumptions, but can't give you citations to them right now because I'm on my phone, I'll see what I can do later.