All combos can be executed while solo, unless you miss or play on dial-up. Sever latency is a pretty bad excuse when you can abuse it to combo while soloing, this is a very slow paced game and its very easy to predict how something will move when you are solo. Most mobs don't dance around like cactuars do, and mobs don't instantly move when you do, this is your window for solo directional combos. If you need to initiate the WS from behind, run through it and WS from behind. Combos have a timer, after you have hit it from behind and need to now hit it from the side, wait for it to face you then move to the side and WS when you are at that point.
The only reasons I can think of for not being able to combo while soloing is fighting while locked on to your target, or you just need more practice.
The Natalan Sentry for Sent Gauntlets is a great solo target because you cant fight it relatively safely and it has enough hp to get a good number of combos off.