It certainly won't hurt being strong If you're too weak, technique wont help you much against the most basic strong fighters anyway...
You got it at the wrong end there bud.
The trick of tae kwondo is using the strenght of your oponent against himself.
So the stronger and heavier or bigger he is.
It only becomes easyer to kick his butt

Only there's one point what is pretty important though.
If your oponent is very strong, it would be wise to stay out of his arms

But when you master your techniques, it won't be that hard to dodge a slow powerfull guy.