Sorry to hear that, but also kind of glad I'm not the only one 

  That's how it is for me most of the time.  I did DIY for a while to save money, but having non-premium liquid meant half the time I was pretty much tasting nothing at all - even when mixing recipes that people were raving over.  So I've gone back to buying proper juice where I can generally taste at least something nice, even if it's only one out of four of the flavours that the description and the reviews state should be there 
 
I try to always have at least four tanks/mods on the go, so that I rotate flavours each vape - that helps keep each one more flavourful.  If I keep vaping the some one exclusively, I lose the taste of it much faster.  I've got five on my desk right now.
Have you tried any of the 'fancy' coils?  Like Claptons?  When I first stated vaping I tried a few fancy ones - lots of different twisted wires (Kanthal at the time), and even some of those crazy coils that RIP Tripper on YouTube shows, like the Diamond Coil.  Never noticed a difference in flavour.  Now I keep it simple : 2x twisted at most, and that's usually only for Resistherm which is only available in 29G.  With Titanium I'm just using simple 26G, 8 wraps.  I do keep meaning to try a Clapton sometime, as so many people rave about it.  I expect to be disappointed though.
Nor have I ever noticed a huge flavour difference with RDAs.  When I first started vaping I got the impression that RDAs were meant to be the ultimate for flavour.  But now I wonder if that was simply old info, comparing them to cartomizers or the old crappy Nautilus type tanks.  I can get OK flavour from my Magma and Lancia RDAs, both of which have under-coil airflow, but it's never better than my good flavour tanks - Aqua SE, Aqua v2 (clones), Goblin Mini, and others.   I figure that nowadays RTAs should be the ultimate for flavour because they all have under-coil airflow, and they have much smaller chimneys so there's more opportunity for the airflow to concentrate the vapour.  Maybe I've just not found the right RDA, but I'm yet to find one that I felt was giving unusually good flavour whereas the RTAs can sometimes do that (though it's incredibly variable for me, and I still have no idea why.)
If you haven't tried the Aqua SE (authentic only, $80) or Aqua v2 (clones from $25) I can highly recommend them as great tanks all round, and great for flavour particularly.  And I've been quite impressed with the new Goblin Mini by UD - it has an unusually wide airflow slot, so unlike most other devices you get airflow across the whole width of the coil, even when it's spaced and/or big.  And a compact chimney.
Hope you find a good solution for your SXK TC, though it's never going to be particularly smooth I'm afraid.  More metal and therefore more residual heat does sound like a good idea to try.