The phrase "brutal taskmasters" can be a harsh description for someone who demands too much from their subordinates. There are various synonyms that can be used to describe such a person, including strict, harsh, unforgiving, severe, unyielding, and demanding. These words highlight the difficult nature of the taskmaster's expectations. Other words that can be used include rigorous, draconian, oppressive, rigid, and uncompromising. These terms suggest a level of rigidity that can make it difficult for anyone to work under such a boss. In conclusion, the phrase "brutal taskmasters" can be substituted with a variety of synonyms, each painting a vivid picture of the challenging nature of such a person's demands.