The problem I've found with assassin is they have no AOE attack, all their attacks are focused on one target.

I've found shadow shift situationally useful early-midgame to port yourself over and swap places with a spellcaster so that the rest of your team can demolish him.   It does leave you in kind of a bad spot of course.   I usually don't bother with it anymore.   I've never used hobble, it was/is still? bugged at one point.

I usually go the dodge line for defense first.  then critical strike line /eviscerate / ignore armor line

Also, I would be interested in any feedback on these ability ideas.....

1) Sneak Attack (or similar name)

Would autocast at the start of tactical battle and do damage against against a random target (before anyone moves).  No idea how much damage exactly.  Possibly it could also knock the victim prone and/or stun them.

Most likely it could be handled as multiple abilities... so a trait to unlock the ability, then one or two subsequent abilities to make it more effective (a bit like the way bleed I, II etc work).

2) Assassinate

A relatively short range strategic attack (spell), like cast it at a unit 3 or 4 tiles away.  It would cost no mana, so would have to have a cooldown to stop it being repeatedly used (like 10 turns or something).  Target a single unit, and it would have a chance of causing damage (maybe a critical hit worth of defendable damage).  Not sure what the "chance" would be exactly... again this could have a base ability to unlock it then 1 or 2 traits to get better at it (better chance of success, more damage etc).

Possibly with this one the Assassin would have movement reduces to zero for a turn or two afterwards.

With both of these abilities.... one way to go would be to have it so that there is a chance the Assassin is injured (takes damage) in the process.  So maybe the Assassinate ability would have a base chance of success of 50%, 25% chance nothing happens, 25% chance the Assassin is hurt... to represent them making an assassintation attempt, and being caught and injured in the processes.

On another note, I'm tempted to give the Assassin Immunity to Swarm as a late tree skill... would be handy for a lone assassin and maybe help them survive, but I dunno.  Not sure if overlapping stuff like that (Defender has it obviously) is a bit boring.

Cheers.

Sorry I probably should have made it clearing in the post (will edit it now).... I'm talking about a strategic spell, like 3 or 4 tile range.

The Lethal traits and the Executioner traits are cumulative. At Lethal III, you have +12 physical attack, not the +5 listed on the trait - you get +(3 + 4 + 5) from having Lethal I + II + III; same goes for Executioner and every other set of traits available. I certainly agree that Lethal is more useful than Executioner, but you're underselling Lethal here. Also, as of the last point in time anyone brought this up, Stardock said that this kind of stacking was intentional and that they were open to suggestions as to how to show it better. Nothing ever came of the thread about it, though.

I would suggest combining these with some kind of critical chance or critical damage bonus, or perhaps a small general damage bonus - if you're more accurate, surely you can find the weak points more easily in addition to hitting the target more often. That, or make it be more of a side branch than one of the primary branches of the tree.

If you do the calculations, +3 attack on a base of 10 attack is effectively an average damage bonus of ~50% against targets with defense ratings from 0 to 40 (the actual bonus goes from 30% against 0 defense up to about 60% for 40 defense, using a base attack of 10). Linked below is a calculator - put in a value for the bonus in the cell B1, and the decimal form of the percentage bonus over the base attack scores listed in column A will show up in the row and column corresponding to the basic attack and defense scores your unit might be up against, while the right-most column contains average percentile damage bonuses from the attack boost for the given attack score (and the bottom-most cell in that column gives the overall average damage boost for all attack/damage scores in the spreadsheet):

https://www.dropbox.com/s/2b6pzfducv9lhy6/BonusCalculator.xlsx

You will need Microsoft Excel 2007 or higher, or a compatible program, in order to use the calculator. If you want to calculate it yourself, the increase in damage over the unboosted attack damage was calculated as follows:

%_Boost = 100*{ [ (A + D)*M*M(A + B )*(A + B ) / ( A*A*[M*(A + B ) + D*(1 - P)] ) ] - 1}

which is a simplification of:

%_Boost = 100*{ [(A + B )*(A + B )*M*M / (M*(A + B ) + D*(1 - P))] - [(A*A) / (A + D)] } / { (A*A) / (A + D) }

In these formulas, A is the base Attack score, D is the Defense score, and B is the magnitude of the bonus applied to the attack score. M is the decimal equivalent of the percentile attack bonus (25% bonus => M = 1.25), and P is the decimal equivalent of the armor penetration (33% => P = 0.33).

Edit: I put up a new version at 9:55 EST that allows you to see the effective bonus when you include armor penetration and percentile attack modifiers, in addition to the effective bonus when you include additive attack bonuses. Give the percent bonus as an integer, unless you want to see the bonus for e.g. 0.25% attack bonuses; same goes for the penetration. The spreadsheet now also lets you choose the increment and the initial value that you want to start the computation at without going in to modify the cell formulas.

I also modified the formulas given above to reflect the changes made to the spreadsheet.

Oh, and Armor Penetration is bounded between 0 and 100 in the cell formulas doing the computation, because in-game you can't have more than 100 armor penetration, and I don't see the point in giving weapons negative armor penetration (well, I suppose if you wanted a weapon that was intended for use vs unarmored targets, but still ...).