try throwing away your portals first. They're super heavy against performance. Instead use a separate list view to display the related data and improve your navigation back and forth between the two layouts.
Also, you might want to further optimize your data by removing unstored calculation fields and summary fields if they exist in a great number.
For example, if you load a single record and 25 related, you're loading ALL fields for those 26 records, regardless of what's on the layout.
You described a simple database, but if you didn't optimize your schema, it could be detrimental towards moving your file to webdirect.
I think we tried that once in the past.
Since the list holds the same data I think to remember that we saw no significant improvement.
Mike gave you some good suggestions. WebDirect layouts really need to be made as light on code as possible by sticking to themes and only putting what is needed on there, and avoiding things like portals and tabs. These are cool things, but they don't work so great in WebDirect. These types of things work much better with FileMaker Pro. I've worked with two clients who did what you did and went all WebDirect. Both of them went back to using FileMaker Pro application clients for their day-to-day FileMaker users. I think WebDirect is getting there and is the direction of the future, but I have found few full time users of FileMaker that have been satisfied with WebDirect compared to the FileMaker Pro application. Light duty and occasional users seem to be more successful with WebDirect. FYI, 5 users on WebDirect is much more demanding on FMS than 5 FileMaker Pro users because the server is thinking through all of the UI work and not the client machines.
An alternative is to go to Custom Web Publishing which will be faster than WebDirect, but involves a lot more work.
WebDirect can be made to work, just don't design things like you would for a FileMaker Pro client. As developers, we have to think differently when we design for WebDirect.
the reason we use Webdirect is that our customers prefer to use webapplications.
They don't want to be bothered with local server installations or FMP client installations.
I agree with you that Webdirect will becoe better and better.
Another thread is making a whish list for FM15.
Filemaker, if you monitor this discussion as well: performance, performance and performance!
There was a (verifiable) 25% performance gain between 13 and 14. That's huge on FileMaker's end. It's a two-way street though, you still should investigate to see if there's anything you can do better on your end. Hardware is a part of that, but every system I've mentored on or converted for WD has had at least a few things that needed improvement.