Its viable for pvp...not so much pvm as u'd really need more options for healing. But for pvp u can couple EP with eaters on ur suit (pots for a quick refill and eaters once ur hidden to slowly regain back the health - add in HPR if needed as well to help with regaining health). The biggest downside to having fencing (as far as pvp is concerned) is the necessity to be next to your opponent to deal damage. I personally prefer archery for my stealthers just because I don't have to be right next to someone to dismount them when team fighting. The days of solo killing someone with a dismounter appear to be over. 1 in 100 do I get the chance to kill someone without someone else being right next to them. and 1 in 1000 does that person not have ninjitsu to just wolf form away.
As far as stats...I would probly run 125/100/35 (if u eat up all points needed to have 260 - if not, take from int - and be an elf for the +20 mana). Try to get dex to 125, int to 70+ and any other room to str/hpi. Fencing is fast class and u don't have healing so 150 dex isn't really needed.
For stat values I'd probly run something to the affect of 120 anat, tac, fencing, stealth, 110 ninja, 100 hiding, 80 poison (would be 770 - so either legendary ring/brac combo that supplement skills or drop 50 points to get 720). If you had archery you could get the VvV HH for +20 archery
(just saying).
The main reason for an archer is (once you dismount your opponent) they have a couple seconds before they can remount or wolf away. if you're fencing then you have to hope you catch up to them running to deal another hit (barring they're running until they can wolf or remount). With archery you pick any random spot where you're in range, and after dismounted you're both on foot, the downside to them is you dealed massive damage with a heavy xbow and now are using moving shot as you're chasing them, effectively destroying their bandages and killing them or if they're only pots they used them after the xbow hit and are now vulnerable for roughly 5 secs. I have 3 archers - 1 is an archer/fencer. So I'm a little biased but for good reason. Hope this helps!