It's possible but not very ideal, which is probably the reason why there aren't any guides for it.
One issue is that a berserker's damage largely depends on stamina and the templar spec mostly has activated abilities that use up stamina. So berserkers tend to benefit from stacking on damage and attackspeed passives and relying on autoattacks, whereas non-berserkers can stack on sustains and deal spike damage via abilities. In this regards there simply isn't that much synergy between the berserker and templar specs.
The other issue is that reaver and post-patch berserker completely outclasses templar in terms of increasing dps. Since DA2 combat tends to favour dps-focused setups, there isn't much of a reason to go into the templar tree outside of roleplaying (I personally only get the +10% damage bonus for non-berserkers). Templar abilities are largely focused on preventing damage by silencing (preventing their use of abilities) and removing their buffs, which is largely unnecessary since it's better to just kill them instead. That said, holy smite is reasonably powerful, so the spec isn't totally useless.
So, with that disclaimer, a berserker/templar S&S build could be approached as a weakened berserker build (focusing on autoattacks, but losing out on some extra damage and attackspeed) or a weakened 'non-berserker build' (focusing on dealing spike damage via abilities, but losing out on extra damage).
- Berserker builds firstly involve getting enough strength for a reasonable attack, then focusing on increasing willpower for superior gains in base damage. Some of the weapons with 'enemies cannot dodge attacks' can be useful, but from memory, the ~45 strength to wield end-game weapons is usually sufficient.
Dps-wise, cleave, the berserk and might sustain will be the main source of extra damage. (Might will reduce base damage, but the damage bonuses will usually be worth it until late-game). Along with barrage and (dual) haste from allied mages, auto-attack dps should be reasonable.
- Focusing less on the berserker side of things, increasing strength alone will reduce the amount that damage is impacted by ability use. Since sustains take up proportions/percentages of stamina, willpower can be left quite low to reduce the amount of stamina 'wasted'. The only downside is perpetual stamina issues, especially since autoattacks will take up stamina if the berserk sustain is used.
Damage can be increased once again with cleave, might, and potentially the bravery sustain (which takes a boatload of stamina). Activating the berserk sustain might be useful in terms of using berserker abilities. Not needing to maintain a high stamina also opens up options for tanking sustains.
In both cases, popping off lots of CCCs such as scatter and assault will probably be optimal.
That is,
- Draw threat with S&S warrior to get enemies clustered around it - ideally via high dps+proximity, with goad+armistice (and possibly taunt) as backup
- Get rogue to disorient clustered enemies with fatiguing fog (and/or confusion)
- Explode all the disorientated enemies with scatter and assault CCCs - mages can also can use spirit bolt and stone fist CCCs
- (Non-nightmare) If friendly-fire is not a concern, working in a walking bomb CCC will definitely make up for any damage deficits
Additionally,
- Stagger elite/boss with pommel strike and/or shield bash
- (Non-nightmare) Get Isabela using lacerate to use explosive strike CCC or twin fangs on staggered elite
- If friendly-fire is a concern, use chain lightning or crushing prison CCCs instead
Lastly, as per usual, mages should keep up heroic aura and haste, crowd control elites with winter's grasp/petrify, archers can use pinning shot to crowd control elites and archer's lance on brittled enemies, and on non-nightmare, dropping firestorms and/or hail of arrows will add to the overall damage.
At this stage, I still haven't really mentioned any Templar abilities. Aside from spamming holy smite at mages/demons/whoever, from what I've heard, silence is great to prevent assassins/rage demons from stealthing/backstabbing, and cleanse can be used to remove the buffs from commanders/desire demons.
Also, if you have the edge of night axe from the dlc item pack (and aren't playing on nightmare or don't mind switching weapons), equipping +%spirit mage gear will boost both your weapon damage and holy smite damage. Unfortunately, the patch made it no longer possible to have an allure's crook templar haha (http://youtu.be/c_WjUJD_oI4?t=1m16s)
Not much of a guide, but hope this helps!