It may very well be an unpopular opinion and not the intent of the Dev Team, but the -guard function the shadow has, seems a bit immersion breaking. The fact that it can work against ancient liches and dragons alike, but come a player-character, and it becomes almost entirely useless, just really doesn't sit well with me. Sort of a weird disconnect, when logically, one has to wonder why it doesn't work? Especially considering, as shadow dancer currently stands, it's VERY GOOD at pve. Too good, I should think.
Now, am I saying -guard should work in PvP? Absolutely not. I honestly feel like -guard shouldn't exist at all. I don't like mechanics that exclusively work in pve or pvp. Strays more into the realm of MMO mechanics, than Persistent World mechanics.
So alternatively? If having close proximity with the shadow can grant sneak attack, what about the feats Self Concealment I-V ? At level 3 shadowdancer, self-concealment II, scaling up each three levels afterwards. Self-Concealment III at level 6 SD, Self-Concealment IV at level 9 SD, and Self-Concealment V at level 12 SD. In this way, you just have a non-dispelling form of Concealment, as opposed to almost universal pve mitigation, and zero pvp advantage (bar killing/banishing/distancing the shadow).
Additionally, the shadow could probably use some bonuses to its stealth. For a shadow, it's remarkably un-stealthy. Maybe epic skill focus at its inception (at level three), and regular skill focus / Stealthy feats, at Epic Shadow Lord. Maybe some Discipline foci as well? Beyond this, it's been a blast to see some shadowy character love lately, and I've thoroughly enjoyed the ride thus far

*Drools in anticipation of the shadow mage update*