So in paper it sounds good.. matter of fact to good that some players goes to extend to getting a full compliment of 3. As people are encourage due to the Space Marine Vindicator Linebreaker Squadron box. In my opinion getting 3 Vindicator is a potential risk as you are still binded by scatter die, So in a good roll you can cost alot of mayhem and destruction however in a bad day.. you may be spending a whole turn doing absolute nothing.
Before i give you my take of all this, Here an interesting take on using the Space Marine Vindicator by Fritz40K
So my comment is that he generally placed the unit in extremely ideal environment that you will rarely will get to use in an actual game. Also his take this means to deny your enemy a specific area usually an objective. However it also means that you pay roughly 115 pts(Vanila Codex) doing relatively nothing if your enemy just simply ignore the Vindicator. If you do move him out alone he may get easily pick off due to weak side Av11 armor. So this approach is relatively a dead end that serve some purpose but no where else to go from there.
So my idea is that to send that thing in to generate Aggro, For those who didnt check out my previous entries. You should read it in order to understand what i mean http://w40knoob.blogspot.com/2011/01/aggro.html. A brief explanation is that aggro is the level of threat your enemy will perceive to your specific unit. So example would be a multi melta attack bike likely be taken down first than a heavy bolter land speeder agaisnt an enemy who has plenty of vehicles.
When you field a Space Marine Vindicator so you can divert your enemy attention to that one tank. So you can predict your enemy reaction to your army. Another e.g is if you know u are facing a massive Deep Striking army. With a regular list you are almost uncertain what your opponent may do since you are not sure how he respond. With a Space Marine Vindicator you know that one unit he will do his best to take it out.. so your respond can put him protected and there a high chance that he will come for the Vindicator.
So my suggestion is to place your Vindicator accompany your forces, Make sure you protect his side armor no mather what. So now you force your enemy into a situation. Either attempt to take out your castle up Vindicator or ignore it and risk leaving it alone where it can bite your enemy ass.
Vindicator got a variety choice of additional war gear you can add on.
Storm Bolter: Not bad, since by default it comes with a single stormbolter so you can actually be having 2 stormbolter. So in any case you lose the demolisher cannon you can still do some damage.
Extra Armor: Good addition if you got points to spare, Although you may not shoot but you can at least move to keep up with the army or escape from the danger.
Hunter Killer: Not my cup of tea, Although you can at least shoot something at Turn1-2 as by Turn 3 and onward you be awfully busy with your Demolisher cannon but in my experience it doesnt actually do anything.
Dozer Blade: Poor man siege shield.. Cheap and good addition for the tank as you can charge into dense terrain to get that shot in with better odds to pass that dangerous terrain test. However you are still binded by failing it if given some godly badluck.
Siege Shield: Its a better Dozer Blade.. with a cost of 5 pts extra. It automatically passes any dangerous terrain test. Also it make your Vindicator look more hardcore since u have to assemble the huge plow in the model kit.
Here are some useful types of Vindicator you can use for your army.
Blood Angels Vindi : Fast vehicle so you can move 12" and still fire the cannon.
Black Templar Vindi: 4ed machine spirit.. ignore stuns and shaken