How does suffocating work against someone in a shield, if you are able to get through the shield to choke them, you could slowly stab them with a knife if you want to.
And poisoning would have no effect because of his ability to negate poisons.
And 2 quote from the dune wiki, which strongly implies that shields are possible to have on all the time
Shields can be calibrated to permit the passage of matter below given speeds. This is vital in personal defense shields, as one would suffocate within a shield that did not admit atmospheric gasses. Depending on the shield's setting, the object's speed while passing through the shield would range from six to nine centimeters per second. (shows sheild let air through, so no suffocation).
With the widespread use of shields, anyone of even minimal importance wore a body shield to protect against criminals, assassins, and accidents. Such a practice made the use of projectile weapons and thrown blades virtually obsolete. The only effective combat method was the deft use and careful precision of a handheld dagger, if moved slowly enough. New styles of fencing and knife fighting were developed to take advantage of this one small vulnerability.
Sheilds are used as anti-assasination devices, and as such are useless unless they ARE on all the time, infact (someone with the book correct me if im wrong), i remember the baron had one one that slowed air diffusion of poison gas, meaning that he indeed did have it on all the time.
Also, yes, disabling shields is pretty much impossible, as it requires a shire size static generator, something that would have to be made specifically for the task of disabling the shield (so explosives would be of little use), and which would be impossible to carry through the doorway
also, it is a bit too late now, but i totally agree, when the characters are proposed their abilities and equipment should be specified, to avoid this problem.
and finally where is paul right now? his powers depend on his stage: pre dune he has no prescience and good combat training, before taking the water of life (but with the freemen) he has limited prescience, and post water of life he has pretty much complete prescience.
I think its pretty fair to put him in the second catagorey, which i think would allow him to know when ezio would try to sneak up on him so he wouldn't be able to assassinate him.