This would depend entirely on the dedicated video card you put in the system, but in general, no. A dedicated video card would generate MORE heat, as it would be a more powerful GPU and it would work harder to provide a better display.
Now "most work load is shifted to it"... not accurate. First, are we talking about the newest generation of Intel and AMD processors that have GPUs built into the actual CPUS? Or are we talking about older systems where there is a GPU integrated into the design of the motherboard? Because for the purpose of what you are talking about, these are apples and oranges.
In the systems where the CPU and GPU are separate, but the GPU is part of the motherboard, there is STILL a separate GPU that is generating it's own heat, and doing it's own work. There is empirical evidence to suggest that in an integrated system like that the CPU will work harder overall, but no actual benchmark testing results have been published to prove this.
So, you have a weaker, smaller Integrated GPU producing heat on one hand, and you have the larger more powerful dedicated video card producing heat on the other.
Think of it this way. On systems with an Integrated GPU, you may see a heat sink on it, but you rarely see a fan on that heat sink. Regarding video cards, you rarely see video cards without fans today. Why? They generate a ton of heat.