Sanguine Scythe is also a very important one to have, since it further boosts crit hit damage by a substantial amount.
As for when or when not to weapon skill to proc red/blue, for most NMs if they're casting or doing a TP move, from the moment they start to the moment the animation of the effect ends (or I like to base it on when they take a melee swing right after), you can't proc on them. If the NM is stunned or under the effects of a different proc, you cannot proc them until that other effect has worn off. Likewise, for most NMs that have a two-hour effect, if the effect is active you cannot proc. There are a handful of NMs that have melee swings that count as TP moves (Shinryu, Karkadann, all the Iron Giants, etc) where you can't proc on them if they're swinging, and thus you have to time your attack to go off during the interim time between their melee swings. Lastly, there are a few NMs like Amarok and Orthrus that have certain animations they do (in the case of those two, they'll start howling) that don't appear in the chat log whatsoever. When they're in this animation, they can't be proc'd either.
Lady Jinte wrote:
Vlorsutes' Negotiation Skill rises 0.2 points
Vlorsutes' Observant Parent Skill rises 0.3 points
Vlorsutes' Argument Diffusing Skill rises 0.1 points