While I understand the need for it, I have a problem paying $15 a month on top of the game itself in order to play it. And the game's useless by itself, so if I decide that I don't like the online stuff or it doesn't work for me or it's too much, then the $50 game purchase was wasted.

I see a few potential fixes for this.

1. Don't charge for the online service or make it a lot less. $15 a month is really quite a bit, especially for someone who doesn't have a lot of free time. Maybe have an alternate per-hour charge. Or a per-hour charge with a monthly cap. Or go the Neverwinter Nights route where the servers are user-run but interactable, maybe with a connecting framework controlled by the developer.
2. Don't charge for the game itself or make it a more nominal fee. AFAIK, it's useless by itself, so it doesn't make sense to me to charge for anything more than manufacturing and distribution costs. Making what I assume is a very large client downloadable might be out of the question, but a $5 or $10 charge at tle local shop is probably reasonable.

As it is, I have no interest in paying at least $65 just to see if I like the game, and then well more than that if I want to play it, even if just on weekends.

Of course, MMORPGs are probably cash cows for you guys, so all of this is probably just pissing in the wind.