I think that combat can rapidly drain fatigue from even experienced fighter (especially if multiple combatants is involved). Its only looks like "John hit Z – Z hit John " stuff on the screen, but I’ve always imagine Cata-fight as some Z fiercely grabbing char, char desperately avoiding plague dripping teeth while fighting for his/her life and so on. Not leisure walking among very-slow-and-stupid-punchbags or practicing your kata on dummies. Possibility to die from starvation while killing 1000 Zeds through window seems… not so realistic.
All opinions listed above are good in one way, or another. Its true that combat-nerfing thing should be considered with caution, but strain system, to my mind, is tactical addition, not nerf-the-melee stuff. Encounter with 10-20 Zs should be thing to consider rather than quick “where is my trusted zweihander?”. Reposition, hiding in houses to catch your breath, luring groups of zeds in trap fields rather than chopping them all in one row seems good challenge for me. I remember situation when I found a motorbike and tried to rush through town. I hit the wall, fell of, and became surrounded with 20 or 30 Z’s. I was really scared back then. But quick run to nearest thin passage between houses, broadsword and some slashing quickly changed deathtrap situation (and, possible YASD) to victorious one.
So… I vote for implementation of well thought and balanced strain system (or for increasing fatigue loss in fighting, especially with heavy weapons).