So basically a steppe mammoth.
They fulfill all your criteria
-Front limbs longer than back limbs, big check
-Tusks, huge check
-Long tail, well long for a large mammal, plus there is no reason you could not use a slighlty modified one with a longer tail, just say it is sexual selection.
-Ox like head, well minus horns anyway.
-Similiar in size to Paraceratherium, check (see below)
they already roamed a near desert, the steppe, not all deserts are hot, but adapting them for a hotter setting is easy, elephants already live in the savannah. the ability to find and dig for water makes elephants very good at dealing with dry conditions. the fact they can knock down tree to eat everything on them helps. As a bonus they coexisted with humans so having them still around is not a big stretch.
If you don't want to use mammoths exactly. try basing it on our good friend Dienotherium, nearly the same size, there are several other very weird Proboscidea to choose from.
I also feel I should share some art of someone who has taken a slightly fantasy variant on mammoths you may find appealing.