Blood parrots are not to be trusted; I lost a lot of Clown loaches to a parrot.
I now have 3 NTTs Dats in with my RTG, I only had one up until about a week ago.
The biggest NTT, which I’ve had the longest, is half the size of the RTG. The RTG often goes down to nip it but doesn't attack with much effort. The NTT often shoots out of hiding and strikes the RTG, usually around the gill plates.
Since adding 2 more NTTs, both of which are smaller than the original, the RTG is acting a bit different. The smallest of the NTTs (about 4 inches) is getting picked on by the RTG and it is attacked more vigorously. The NTT is very quick though and seldom gets caught out.
IMHO they're ok to keep together, but if you buy the Dats small they're going to have trouble. They grow a lot slower than Aros.
In addition, I don't think you guys have been buying STs, if you have you've spent a lot of money and bought very mature fish that would have no problems sticking up for themselves. STs are extinct in the wild; there haven't been any on the market for 5 or 6 years at least! What you've bought is (usually) Indo Tigers or Northern Thailand Tigers.