Not only is it a bummer because some people used to use it constantly to keep party members in line, but this also means that there's one less means of communication between all of these random parties forming out there on the realms. Sure, in a perfect world, everyone would know the fights and chat would be enough to make sure everyone was on the same page (or depending of your vision of a perfect world, everyone actually uses the in-game voice chat -- a quick survey of our staff here presumes that it works in cross-realm PuGs, but given that I've never actually seen it used on the live realms by anyone, who knows?), but we're hardly running instances in a perfect world. Sometimes chat is not the best way to get a complicated boss fight organized and ready.
One idea that I've seen popping up on the realms is an addon that would copy a boss strategy for any given instance into party chat for you, just to avoid having to type out "stay out of the fire, run away when you get this debuff on you, etc." all the time. A search on Curse doesn't pull up too much in that vein -- there are certainly tactics addons that will help, but usually they're just warning addons (like DBM), or they require everyone to have the addon installed. There's nothing simple for just putting a strat into chat during a PuG.
Other than that, though, options are limited. You can still mark targets (and in fact, anyone can now mark targets in a party), and of course there are optional items -- flares and such -- used to show placement when needed. But what other options could there be? It seems a little lame for Blizzard to start building some strategies into the interface (though we do already get some automatic raid warnings on major events), but that's probably preferable to spending five minutes explaining the Devourer of Souls fight yet again.