In my opinion, allowing war steeds outside of Rohan seems to be to have been one of the dumbest moves the developers have made.
Since they are faster than regular mounts anyone who has them -will- ride them--exclusively. Even if you like your old horses, it won't be long before the extra speed makes them not worth the trouble. This means non-war steeds are never used except for the most RP'ish, or horsey-ish, players. I haven't ridden any from my large stable of regular mounts in ages, anywhere, where I used to change them up regularly. Now, the cosmetic fun isn't worth the speed hit. And from talking to others, I'm not alone. It has eviscerated the use of all the regular mounts for players that have ascended to war steed level.
Also (though a lesser problem) traveling with anyone without a war steed in lower zones means you have to wait up all the time--there's now a huge disparity in speeds if you happen to be helping a kin mate or just traveling with a lower level player.
They should have simply restricted war steeds to Rohan. Or, failing that, reduced their speed in the non-Rohan areas to make them no better than the non-war steed mounts there.
Instead, they've killed my interest in non-war steeds because I simply never use them anymore, which is a shame, and I'm betting a loss of Store income. They could have had me buying both War Steed goodies and the occasional non-war steed. Now it's only the former. Silly move, Turbine!