I have done pretty extensive research on which travel agencies specialize in DW planning and how much (or how little) they like to be involved (in other words, I know my competition! ha ha). I also know how much (or how little) they charge to do so.
The rule of thumb with travel agencies is "you get what you pay for". If you aren't paying any fees, don't expect the TA to deal with the onsite wedding coordinator, figure our little details like flowers, ceremony details and things like that. They get paid on the travel only, so that's what they will focus on. If they are doing more than the travel and not charging you any fees, they have either marked it up (a common industry practice) or they will go out of business eventually. Clearly nobody can work for free and sustain it.
There are exceptions to this rule. Most airlines don't pay any commissions so if you are marrying in a private property or a venue that doesn't pay your TA commission, there is essentially no revenue at all so a fee is necessary to book the travel alone.
If they are charging you fees on top of their travel industy kick backs, they should be willing to assist you with other details. These fees can range from hundreds to thousands of dollars.
At Blue Petal we decided to do "as much or as little" as our brides would like. We don't have a "set fee" or "packages' because every wedding is totally unique. We sit down with the bride and groom, talk about their dream wedding, how much they want to be involved in the planning process, talk about their budget and negotiate a fee based on how much revenue we estimate will come in from the travel side. This initial consultation is free and we found this works best for both parties.
My advice is make sure there is a clear understanding from the very beginning of what you expect your TA to assist you with. You will likely be speaking to your TA once every few weeks (sometimes way more) leading up to your wedding so find someone who gives you a good feeling and you feel has your best interests at heart.
Ginger ~ Blue Petal