The primary clauses in the Eight Amendment limit excessive bail and cruel and unusual punishment. There is no practical need to ignore the excessive bail clauses because judges have the ability to just not allow bail when they deem fit.
As to the cruel and unusual punishment, America is a nation built on a certain moral code. It is not right to torture people and it can never be justified. Not only is torture morally wrong, it is also ineffective. It has been proved that almost any other method of persuasion works better.
Yes, I think that there is a time when the 8th Amendment should be ignored, because sometimes there are national emergency. When there is a national state of war, and someone has declared war on the United States, they no longer have the protections of the 8th Amendment. They can be tortured to keep us safe.
While torture should definitely be prohibited in most cases, I think that there are times where it might be merited, especially if a detained subject contains information that might save lives. Excessive bail, too, seems like it might be merited if someone like a war criminal is captured -- we certainly don't want them going free if we can help it.
The EIghth Ammendment should be upheld in all cases. The Ammendment was ratified in order to protect against excessive punishments. Those punishments deemed cruel and unusual include but are not limited to, drawn, quartered, public dissection, being burned alive, etc. The Eight Ammendment secures the moral high ground for the governing body. If the United States were to begin hacking people up brutally for crimes no matter how heinous, the Judiciary would lose dignity and become no better than those it punishes. The Eighth not only protects the suspects, but efficacy in the judicial system.