Gimmicks - the love and bane of many players. They can be awesomely fun and really add flavor to a game but they can be unreliable at best and thus will often be shunned or rarely used in a tournament based list. Why? Because relying on a gimmick to help you win a game is bad - you need to be able to control the game and win off merits rather than a single (or several) die rolls happening in your favor. Whilst such dice rolls might be the only way to differentiate between consistently good players with good lists, the basic list itself needs to be able to win on its own merits. Gimmicks can enhance this but do not form its foundation.
What do we mean by this? Let's hark back to the topic of utility or specifically, disruption and blasts. Neither are requirements of a good balanced, tournamet list but having one, if not both, adds some extra dimensions to a list beyond straight up firepower. Now, most lists will have some form of utility. Whether it's simply having a tank which can tank shock or a unit which is less valuable and can bubble-wrap, utility is nearly always built into lists to some degree. Getting further utility often isn't though and the conscious decision to include utility is a great one as long as one doesn't go overboard. Too much of a good thing can become a bad thing and this is quite often the case here.
This is where gimmicks and balance come in. Something like Telion's ability to allocate wounds to whatever model he wants or Corbulo's re-roll are great utility but not classified as gimmicks. They aren't breaking the bank in terms of points cost, they provide something important to the army (Telion gives a scoring unit Stealth and can shoot from a distance, Corbulo is a two-wound FNP/FC provider) and they have that something little extra that can swing a game when that dice roll comes up. When you take these kind of models you're not relying on them to win you the game but their extra ability can do so and over the course of six games at a tournament, that one time can come up and mean the difference between a win and a loss. It is not something you rely upon however and the minute you start to do so, is when your list can start to go downhill.
Compare this to an army sinking 600+ points into utility. For example, the increasing in popularity Writhing Worldscape C'Tan, Orikan and Tremorstave Crypteks, the age-old Shrike bomb or the power armies of the day (i.e. Seer Councils Eldar, Lash Oblit CSM). There are some good abilities and options with some of these units but focusing a whole list around them? It will win you games sometimes sure and it can (and often will) influence the opponent but it also becomes a very rock-paper-scissors based list design and over the course of a multiple-game tournament, you are very likely to meet at least one bad match-up which will generally result in a loss despite any skill disparity in your favor. This is a case of where the conscious effort of taking utility has gone too far and leads to the gimmick label. The units in question might be fine but the over-arching theme of taking so much utility ends up with an unbalanced list which NEEDS the gimmick to be working to win. The inherent problem with this is it will not always work and if the army cannot win without the gimmick because it has invested so many points into it, the army list becomes bad.
Compare this to if we tone such a gimmick within a list back. We'll continue with Necron example and leave Orikan plus two Tremorstave Crypteks as our utility in terms of terrain manipulation. A lot less than before but also quite a severe reduction in points compared to what we had before. There are three overarching consequences of such - 1) the enemy reserves to avoid the first turn terrain effect, 2) the enemy doesn't move Turn 1 to avoid the terrain effect or 3) the enemy moves Turn 1 and is more likely to be hampered by terrain (with the Tremorstaves targeting the more important units). All of these things can be accounted for within the Necron list, during deployment and the first turn. Although no immediate benefit may be registered from such (i.e. enemy reserves or doesn't move T1), the intangibles and the ability for the Necron army to capatilise on them will provide some benefit.
The difference here is the list is no longer relying on the gimmick to work and whilst there is a greater investment of points here compared to say taking Corbulo or Telion, the impact can be taken advantage of on the table without the army NEEDING the opponent to potentially take extra damage from the utility. It is in essence giving the Necron player a win/win situation where the opponent either runs the risk of taking more damage or the Necron player can capitalise on their less aggressive Turn 1. There are still times when this is less useful (i.e. versus a static gunline) but there often opportunity costs for the opponent in relation to this.
Regardless, by keeping the gimmick as utility within in a list rather than one of the main focuses of the list, the army can still function and win games consistently without needing the gimmick to work. When it does, it can mean the difference between winning and losing a closely fought game but when it doesn't, it's not the cause of defeat.
