That guy who said about the crit rate and kept on flaming seems like an absolute retard who should start from www.lineage2.com as a start and read the skills descriptions, after it get some experience in PVP (all of its types) and then think over it again.

As for on the subject:
I was thinking about the same thing and I'm not so familiar with FGracia yet.
COV sounds cool from summoners but not useful for daggers since it lowers movement speed (but sounds kinda cool for some hard oly opponents)
Evasion bonus on lvl 85 with a +6ed armor (aka more evasion) + 4 evasion from archer sub sounds pretty much like permanent 1/2 UE on ^^ so I personally would go for it.
Celestial from WC/(and other who give it, think all buffers do) is a must imo so ye thats the 2nd thing.
THE REAL QUESTION IS:
For 3rd sub ... CP or M.Def ?
700 CP is cool ok I must admit it , improving max CP = even better use for CP pots and harder breaking trough your CP to your HP (but still not that great ... mentioning there are half kills from daggers/archers and the fact that daggers are light armored not like some Tank that can use 700 CP for like 1-2 (more ?)crits (depending on gear buffs lvls and so on , but lets say 1-2 crits to be in the middle ) so prolly that gives you few more normal hits life or a crit (half dmg of the crit) which doesnt sound so great(if not using CP pots aka Oly).
M.Def = taking less dmg from nukes (why maxing CP when you can get even greater bonus from "taken dmg from nukes" yes I know it goes only for nukes and not for the rest physical dds but nukes are not evadable usually (maybe with some skill but yet not sure). ++ M.Def = Debuff resistance as well (atleast the magic curses and debugs, such as Hex, Root , Freezing Strike , Trance and so on.

SHORTER VERSION OF THE POST:
1st Sub - Archer for + Evasion
2nd Sub - WC/other support for + Celestial
3rd Sub - Tyrant/other for +700Cp OR M.Def +?? (sub??)

well, till now i made
tyrant for CP+738 and imho it's fucking awesome
bladedancer for barrier trigger and it's also awesome, it lands pretty often and it lasts from 3 to 5 seconds, plus i can hit while it's active
for the last one i still dunno, maybe UD or evasion or some resist.