As discussed briefly on discord, warlock should have no verbal component during various castings by lore. For some reason, however, the spell silence causes a warlock to be unable to cast any spells and it's nonsense. (be it mechanical or RP side)
Briefly, I'll post what by lore are the warlock's spells.
Invocations: A warlock does not prepare or cast spells as other wielders of arcane magic do. Instead, he possesses a repertoire of attacks, defenses, and abilities known as invocations that require him to focus the wild energy that suffuses his soul. A warlock can use any invocation he knows at will, with the following qualifications:
A warlock's invocations are spell-like abilities; using an invocation is therefore a standard action that provokes attacks of opportunity. An invocation can be disrupted, just as a spell can be ruined during casting. A warlock is entitled to a Concentration check to successfully use an invocation if he is hit by an attack while invoking, just as a spellcaster would be. A warlock can choose to use an invocation defensively, by making a successful Concentration check, to avoid provoking attacks of opportunity. A warlock's invocations are subject to spell resistance unless an invocation's description specifically states otherwise. A warlock's caster level with his invocations is equal to his warlock level.
Now I'll post the definition of spell like abilities by lore
Spell-Like Abilities (Sp)
Usually, a spell-like ability works just like the spell of that name. A few spell-like abilities are unique; these are explained in the text where they are described.
A spell-like ability has no verbal, somatic, or material component, nor does it require a focus or have an XP cost. The user activates it mentally. Armor never affects a spell-like ability’s use, even if the ability resembles an arcane spell with a somatic component.
A spell-like ability takes the same amount of time to complete as the spell that it mimics (usually 1 standard action) unless otherwise stated. Spell-like abilities cannot be used to counterspell, nor can they be counterspelled. In all other ways, a spell-like ability functions just like a spell:
Using a spell-like ability while threatened provokes attacks of opportunity. It is possible to make a Concentration check to use a spell-like ability defensively and avoid provoking an attack of opportunity. A spell-like ability can be disrupted just as a spell can be. Spell-like abilities are subject to spell resistance and to being dispelled by dispel magic. They do not function in areas where magic is suppressed or negated.
A spell-like ability usually has a limit on how often it can be used. A spell-like ability that can be used at will has no use limit.
To that is added another detail for warlocks which are the somatic components, the somatic components for warlocks therefore exist, although they are spell like abilities, they retain the ASF due to medium/heavy armor and shields, but do not have any verbal component.
Because the somatic components required for warlock invocations are relatively simple, a warlock can use any of his invocations while wearing light armor without incurring the normal arcane spell failure chance. However, like arcane spellcasters, a warlock wearing medium or heavy armor or using a shield incurs a chance of arcane spell failure (all invocations, including eldritch blast, have a somatic component). A multiclass warlock still incurs the normal arcane spell failure chance for arcane spells received from levels in other classes.
The conclusion therefore is to fix a bug that has persisted for some time and that is something mechanical due to how NWN2 introduced the warlock class. In my opinion, in addition to making the warlock's spells without verbal components, I would also remove the in game sound or at least, if possible, I would give players the possibility to deactivate them with a command.
Cheers! <3