Dialogue in KOTOR somewhat suggested this was the case. Bastilla constantly warned you of the lure of the darkside, one she wasn't sure she could resist. She took chances misleading and lying to Revan in hopes of using Revan's power for good.
If you needed to stay good to beat the game, then yes, offer seduction away from said path in favor of power. However, I think in a game where both paths have plausible endings, there is an issue of game balance.
If the dark side was considerably more powerful, there needs to be a drawback. Perhaps you weed out, and turn on your companions. Perhaps skills atrophy as you rely solely on the grand power of the Force.