I figured it would be good to make sure everyone can understand how this all works.
Amp is generally more effective in all ways now, particularly in items with CTC Amp:
The 1.6 patches have a string that reduces boss maximum effective DR to 75% (part of the 'no immunities' string) However, if a boss had 100% listed DR, you still needed 25% Amp just to bring that down to the 75% cap; meaning if you didn't have an Amp that was greater than 25%, it did nothing at all, and 26% Amp would reduce them from 75% to 74% (100-26=74).
This made items with CTC Amp often do nothing at all, similar to how in 1.5, an Amp proc would often times not break physical immunity. The immunity is gone now, but you still must 'pierce' through their listed ceiling of DR.
As of 1.6c, most bosses (in Hell) have a ceiling of 80%, which means you will face a 75% damage reduction, but Amp procs from items with CTC Amp add a 10% Amp to the target, which would drop the ceiling from 80% to 70%. This means your Amp proc will indeed increase your damage.
Please note that some bosses you'd expect, such as Radament, Sszak, and Achmel have higher ceilings, and CTC Amp proc (mostly in Hell) will have no effect, and will in fact require a Necromancer with high Amp skill if you want to pierce it, as their ceilings are 90-95%
Nihlathak has also been improved and will not be affected by just CTC Amp procs in Hell, as he has a 90% ceiling. Soulmancer has a ceiling of 99%. Maffer Dragonhand has a ceiling of 150% and is therefor never affected by Amp of any kind. So keep in mind if you are struggling against any of these bosses and are playing alone, you will be better off using a weaken/LT/decrepify proc since the Amp proc will not help you.
The Wraiths and Itchies (ghosts and flies in Hell) also have very high ceilings of 90-100%
I believe every other monster and boss is 80% or less, so any Amp will always help. This of course also all applies the same to Decrepify.
Elemental pierce and Lower Resist/Conviction work the same way. Many bosses have 90-100%+ all resists, and for poison it can be up to 125%. This means with 100% fire resist, you will need 25% pierce just to match the 75% hardcapped ceiling. So 50% fire pierce would be a net gain of 25%. A good rule for this patch is to aim for 100% (or 125% for poison) pierce if possible to be sure that you're bringing all bosses down to at least 0%. It will be difficult to obtain those kinds of numbers but with runewords/facets/gems/etc it's not impossible.
Another thing to keep in mind is to make sure you double check the runewords in the webpagemaker item list in the
INSTALL POST before you make them!!! Also, the runewords there aren't listed in any real order, so you'll find your options easier by just doing ctrl+F and typing "staff" or "missile" or "torso" and then hitting F3 to search through the list.
I hope this is helpful for everyone!