Thusly "Bill Stock" Spake Unto All:

The problem isn't that the otos might hurt the tiger barbs, the
problem is that tiger barbs are aggressive b*stards, pretty much
guaranteed to harass/hurt/kill any shy & peaceful fish they're kept
with - like, for instance, otos.

Yes the T' Barbs were definitely a PITA when I first got them. But since I
added a few more they tend to bother each other, rather than the other fish.
They occasionally chase the Loach, but he tends to hold his own.

Once they've killed off all the easy targets, the slow, small, timid
or long-finned fish, you get to a kind of peaceful plateau - until a
fish to show signs of weakness, for instance become ill, then they'll
pounce.
They only attack fish they perceive to be defenceless.

Tiger barbs were the reason I stayed clear of everything barb for
almost 20 years. Ironically I have since found that the wretched tiger
barbs are in a class all their own, and pretty much all other smaller
barbs are good community fish, and usually better-looking to boot.