With issues like this, I find de-query (from the data subset menu for the view) will often solve the problem. This stops filters on certain fields affecting the view.

There are, however, cases where the ability to de-query within a formula would be useful.

Regular formula fields are calculated in terms of ALL DATA already. There is a need to allow you to configure formulas to calculate for the view's (typically filtered) data instead.

See: http://forums.visokio.com/discussion/868/is-there-a-way-to-make-subset-work-on-filtered-datas/p1

But this is the opposite of what you're asking. I assume you must be using one of the following places you can apply formulas:

• In-view aggregation, with "(formula result)" selected (as per workarounds described here)
  
• Formulas in Content View, and also view headers/footers and page headers/footers
  
• Formula measures in the Bar/Line view and other forthcoming new views in 2.8
  

In all these cases, formulas are recalculated in terms of the view's data. Bar/Line formula measures are further restricted to the 'bucket' of data being 'measured'.

There is currently no way in such a formula to "reach outside" of the data subset being calculated and obtain results from filtered-out data, aside from changing the view's "Data Subset".

I have reclassified this as an Idea - the ability to access data outside of the calculation context, through some extension of formula functions.

This is exactly what I would need for my tables. Are you still considering this option ?

Yes, although it doesn't have much popularity. More likely earlier is the ability to configure a view to recalculate its formulas, instead of the workaround here:
http://forums.visokio.com/discussion/comment/2200/#Comment_2200