Ring of Fire,
Dath's is one base i've never tried. i did pick it out in the early days but somehow never got round to it.
in terms of what a base should taste of is a very difficult question to answer - they all taste different. the important things is that they pass a threshold. when they do the difference in the final curry is not that significant and is affected more by what goes in and what is done at frying/cooking stage.
i have no help to offer on how to measure "threshold". it's very clear once u've cooked a curry with a base that does not pass muster though. for me u have to make several bases and u soon get a feel for it. for me the threshold means that the base is in balance with nothing standing out yet it has a depth of spice. it's almost a finished curry but not quite there. it should taste good and be quite thin in terms that there is excess water in it (this evaporates at the frying stage). u should be able to see a lot of texture in in though at the same time. the closest comparison in normal cooking is a thin soup.
i would start with BE's base. it's pretty good. not tier 1 but there is much learning there.
links:
https://curry-recipes.co.uk/curry/index.php?topic=2815
,
https://curry-recipes.co.uk/curry/index.php?topic=3074.0;topicseen
if u have specific questions just say. after BE i would go for something like saffron/SnS2008/Admins, then say the ashoka. that sort of tour would give u a very good appreciation of what makes a good base and more importantly what u're personal preferences are eg i like fresh coriander and coconut and add it to all bases.
as for u're existing batch - just knock up a curry and see how it tastes - all part of learning this tricky game. the cooking part for me is at least 50% of the jig saw.