Hi, I am actually playing an Argonian Assassin at the moment (lvl 20 atm). I am playing on normal difficulty though.
My stats atm
Stealth - 70ish
Light Armor - 45ish
Alchemy - 40ish
Archery - 40ish
1H - 37ish
Since my sneak levels up so easiliy (from sneaking, backstab etc) it means the other skills are left behind and hard to level them up naturally. If I was to do again I would focus more on getting archery/light armor/1h up earlier by grinding.
Strengths of build
Can 1 hit almost anything if you can get in a sneak attack (30 x damage with Dagger on backstab from Sneak perk + Dark Brotherhood Shrouded Gloves)
Sneaking is very effective for dungeons or avoid confrontations in the open, especially at night
Sneak attack with bows also effective
Posions are awesome...paralyze poison ftw
Weaknesses
Weak in open fights with tough enemies (trolls etc). I duel wield 2 swords in open combat and only wear leather/shroud armor (for RP reasons, cannot play an assassin in elven/glass/dragon armor sry). I am hoping this changes when I get my 1H skill up. Also I am trying to get the Ranger perk in archery asap as then I can move faster (i.e backstep and shoot) hopefully giving me an edge against tough enemies.
Animals such as sabre cats/cave bears/trolls etc are annoying as they are very hard to backstap (as they do not stand bloody still) and can be a problem.
I do not dabble in magic unfortunatly as I have to concentrate on raising my core skills first. I think those above take around 40 - 50 perks points so alteration or illusion magik might be worth a look after.
I have to say though assassination missions rock and generally going around dungeons sneaking and taking out all the enemies silently is awesome
Anyways hopes this helps somewhat. I do not claim this is a great way of playing, but it is one I enjoy (even with it's short comings) and I guess that is the most important thing
