you are correct in that the damage that you saw increasing from rank I to X stays at the X level in rank XI where you now get the new weapon variant modifier stat kicking in..
So your base damage as such will not increase in the usual sense that you see it in the main stats. So your base damage for the weapon will NOT increase as far as i can make out from I to X of the variant weapon.. what does change is the variants effect modifier (although i am not seeing any incremental change in siphon weapon at the moment from the UI.. so am not sure if this scales or not yet)
Bulwark:
The only thing you are getting from Bulwark weapons is increased damage resistance when you are near other team-mates. (this naturally increases depending on how many other team mates are close-by) This will be most useful if you are doing the upload and you are not capping it with a stealther.. so if for example 2 or more people are with you in the upload circle then bulwark will give you increased damage resistance meaning incoming fire will damage less in proportion to the number of people near you. I believe his 'should' stack with any existing resistance value you have using skills so should make survivability in those sticky upload waves even greater.
Concussive:
The damage you do with the weapon will be the same as your rank X weapon, but killing that enemy via its Weak-point(s) will yield a biotic explosion that will then explode for the amount of damage shown per level for the concussive weapon. If you kill an enemy via anything other than its weakpoint for the 'finishing shot' it will die normally and no biotic explosion will be seen.
Siphon:
This is exactly as it sounds.. it leeches health from the enemy and gives it to you (how much will depend on how much damage you do to the enemy, so hitting weak-points is recommended for maximum benefit).
Hope this helps, this is based on what i've been finding so far and am happy if anyone wants to chime in and add or amend details.
Basically it is a very comprehensive thread about the new weapon (types).
But the Syphon table is incorrect since it doesn't display the increase of life leeched/syphoned per weapon level.
A level X Syphon weapon has 3.75% damage returned as health.
(and the level in-between % accordingly)
All the other Syphon features seem unchanged.
I'd noticed the stats hadn't increased,for the first 5 levels of siphon when i first did the stat sheet, so figured it was a UI issue, i've noticed just now though that they now DO display differences for dmg returned as health. will update my siphon chart shortly.
*edits to siphon chart done*
