How cheesy is it to ignore an enemy unit?

Played a game yesterday.  My Empire vs. Dwarfs.  Battleline scenario.  As we were doing alternating deployment, my opponent placed a block of thirty giant slayers and an equally large block of clainsmen on the far end of his battleline.  I had been planning to put my knights or demigryph knights at the corresponding end of my battleline.  But once I saw that slayer block, I packed everything into the other end of the board.

Long story short, the slayers and clansmen never got to engage anything except a ten man handgunner unit.  And my two knights units routed the ironbreakers and longbeards along with his general, a rune priest and a thane at the other end of the battle field.

What really won me the game was his lack of armour penetration when attacking both my knight units.  I only failed a single 2+ armour save between both knight units all game.  It helped that both his cannons misfired turn one with the result that they also couldn't fire on turn two.  I also got pretty lucky with my lore of metal magic rolls.  Only miscasting once, and my ward save blocked the result.

Regardless it seems kind of cheesy that I just flat out ignored the slayers and clainsmen units at one end of the table.  Those units were a significant percentage of his army's points.  I try not to play "win at all costs".  I want my opponent to have fun.  At the same time I am always trying to win the game.

I just feel kind of guilty that the game turned out so massively lopsided.  We didn't work out victory points.  But It was probably the most lopsided victory I've ever seen in Warhammer.  I routed everything except the slayers and clainsmen that I ignored.  And I only lost the single ten handgunner unit, plus a few guys here and there.  Oh and my rocket battery that blew itself up turn one.  That was the only bad dice result I saw all game.