佢哋嗰啲 = 他們那些
我哋呢啲 = 我們這些
佢哋嗰啲喺政府工作嘅人 = 他們那些在政府工作的人 = Those of them who work in the government
我哋呢啲喺政府工作嘅人 = 我們這些在政府工作的人 = Those of us who work in the government
嗰啲人 = 那些人 = those people
嗰啲喺政府工作嘅(人) = 那些在政府工作的(人) = Those (people) who work for the government
Does 佢哋嗰啲 ever sound more redundant than 嗰啲 or 佢哋 by itself?
If you think 他們那些 sounds redundant compare to 他們 or 那些 by itself, then yes. However, 佢哋喺政府工作嘅人/ 他們在政府工作的人 and 嗰啲喺政府工作嘅人/ 那些在政府工作的人 have a different emphasis.
佢哋/ 他們 emphasize 'them' in specific (we are talking about a specific third party - you have some people's faces in mind)
嗰啲/ 那些 emphasize 'those' in general (we are talking about all or any third party in general)
佢哋嗰啲/ 他們那些 emphasize a specific third party along with all or any third party in general (they and people like them)
The Cantonese sentences in this post are all colloquial. The Cantonese language writes in Standard Written Chinese (SWC) which is almost identical to written Mandarin.
Written colloquial Cantonese is not considered official or formal. Most of the time you find written colloquial Cantonese in social media, comic, comedy or tabloid