thanks for sharing your problem. First of all, let me recap your issue: you would like to move IPAM to separate server because your users are complaining about Orion server availability correct?
There is no global answer to your question if it will be better to run IPAM as a standalone or as a module. But let explain what could be benefits of these two options.
Btw, IPAM 3.0 has been released recently (http://thwack.solarwinds.com/message/170783#170783) I'd recommend to do an upgrade to get rid of bugs or performance problems".
Now, running IPAM as a module together with NPM or UDT on the same server will give you the benefit of having shared database for nodes, alerts, etc. which makes your configurations global, faster and easier to maintain. Also you can set user permissions globally for all product you are currently using. Biggest benefit is correlation of information coming from NPM, UDT, Netflow and IPAM via single webconsole.
Having IPAM as a standalone installation on a separate server has an advantage in dedicated database and web server (no impact of other modules and you will also probably won't have so big web load -> better web response time).
It's matter of choice, there is no global rule saying when you should apply which kind of installation.
We do believe that having everything on a single server is always better than distributed installations. Mainly from set-up, maintenance and data availability perspective. We also offer the "Additional Web Server" package which can help you in case of low IIS performance or the "Additional Poller package" that can help you with polling performance.
I'd keep it on single box with the rest of the products because that will help you keep all the information (networking, IPAM, application) together and I'd probably try to figure out what is the root cause of user's complains and if there is a possibility to eliminate that.
please let us know if you have more questions.