(Played 1.x before any real patches came out, and have played WoW since vanilla, skipping only Mists raiding and mythic WoD)
The combat does not differ significantly enough nor align itself enough with WoW for me to give many points of comparison. In most ways it was simply worse, in my opinion. It could have easily taken an alternate step to something rather great rather than its 1.2 streamlining, which I then would have likely considered about equal to whatever period of WoW combat you consider best between now (WoD) and BC. It did not. The combat differed primarily only in that more white attacks (originally things like "Light Slash and Heavy Slash, later replaced by auto-attacks) were required to do any real attack, and the real attacks therefore hit for proportionately more. There were originally more damage types and distribution models (pure circular AoEs, circular progressive cleaves, donut circular AoEs, linear dmg-increased-per-hit AoEs, pure linear AoEs, linear damage-reduced-per-hit AoEs, and so forth), and each 'class' (little more than a weapon, with particular damage models) shared abilities with nearly all others upon learning, such that you had more to pick and choose from. (Open with Pummel, Circle Slash, Brandish, Aura Pulse, Trammel one side, Jarring Blow counter the other, bottleneck and psuedo-kite into Doomspike... maintain heavy on lead mob and do switchbacks behind it as a shield while generating TP for the next burst... all on a Pugilist. That kind of stuff.) Arguably, that's not especially different from any other tab-based MMORPG's combat system. The difference quite simply lied elsewhere, unless you wish to look at other directions Tanaka's combat system easily could have gone in that would prioritize damage-type/form synergy (more loose-arsenal), rather than maintaining key rotations (more fixed even than WoW) as per Yoshida's. That may well have differed. Alas, we'll never know.