Have you looked at the percentage of queries that agents are accepting these days? Many agents are taking on an average of one client for every thousand queries or more that they receive. Do you really think all of those other 999 writers had serious problems in their work, or had no clue how to submit?
With odds like that, exclusives are a serious problem.
The moment you start thinking about odds, you lose. Percentage has nothing to do with it. Odds have nothing to do with. I don't just think those 999 writers have serious problems with queries and actual writing, I
know they do. I've read far more than my share of slush piles, both in query form, and in actual manuscript form, and I've gone months without finding a single writer who had a clue, especially about how to write a good query. Finding a good query is extremely rare.
Finding a good manuscript isn't much easier.
A certain percentage of good queries and manuscripts do get rejected because of fit, and an even smaller percentage because of simple oversight, but fit is something that's in the writer's control, and those tiny few that an agent or editor simply misjudges have no trouble at all finding a home elsewhere.
Going by odds is just wrong. The only way odds would matter is if every query and every manuscript had equal value, and an agent or editor selected what they wanted at random.
But here's the thing. I don't know of any agent who asks for an exclusive on a query. I don't think sending out big batch of queries all at once is at all smart, and when a writer tells me he just sent out a batch of a hundred queries I can be pretty certain every agent will say no. Certainly the good ones will.
Agents ask for exclusives on the actual manuscript, so even if going by the odds made sense, which it doesn't, you still couldn't apply that one in a thousand rule. When an agent or editor asks for a partial, or a complete manuscript, you've already jumped one big hurdle, which is getting their attention.
It just isn't smart to place an unneeded hurdle in you path by not granting an exclusive. Either this is an agent you really want, or you shouldn't have queried her in the first place. If you don't want her, don't query her. If you do want her, then play by her rules. She has them in place for good reason, and they're to your benefit as much as hers.
The surest way to waste time is by turning writing into a numbers game, by looking at the odds. The surest way to save time is by giving agents and editor what they want,
the way they want it.
There aren't many really good agents out there for a given genre, and a poor agent is worse than no agent at all. If you want one of the good ones, you have to stop looking at numbers with no meaning, and concentrate on giving them what they want, the way they want it. Do this, and you'll land an agent and a publisher. Fail to do this, and you can spend years without landing either.