A bit of background, I threw a group of Eldar Exarchs at my PCs lead by the Farseer from LotE as a revenge/fulfilling destiny scenario. I didn't want any of the Exarchs to die, as they were just to try and enforce a 1 on 1 fight between the Farseer and the Rogue Trader, so I gave them all force fields. Almost right before this all of the PCs had picked up force fields as well.
We get into combat and the fields are blocking almost everything, and the 2 hits they don't block are brutal. The Astropath goes to -7 wounds and loses an arm and one of the Exarchs goes to -11 wounds from an inferno pistol in one seriously unfortunate series of avoidance rolls. In 3 rounds of combats roughly 95% of all attacks were either parried, dodged or blocked by the force fields. There was 1 Power Field and the rest were Eldar Fields. I saw this as appropriate, but a few of my players were slightly unhappy, saying that the combat was dragging on and it seemed like no one was really in danger. It was also pointed out that a single field was worth more than Step Aside + Wall of Steel + 4 Agility Advances + 4 WS Advances. The lower the field number, the more perceived balance exists as well according to my players.
To fix the perceived problem, I said I'd come on here and figure out a bunch of suggestions on how we can modify the Force Field rules to make the combat a bit grittier. If you could review and give opinions about my suggestions, and even give additional ones as you think of them I'd be very grateful. My next game is in 2 weeks and I'll post a follow up afterwards.
1) Change nothing. RAW, use the same overload and negation rules as in the book. The two hits that got through either nearly killed the person the receiving end, or DID kill that person. If that's not brutal enough for 40k, I'm not really sure what is.
2) Have the fields only count for one hit in a round. Maybe from any given source. Much more brutal, really makes the shields not worth their rarity.
3) Have them become more prone to failure. This one has several sub options, and therefore is the one I'm favoring the most. They also only count for that single round of combat to represent a field collapsing for a short period of time. Precedents include Void Shields and the rules for the Titan Void Shields from Rites of Battle.
3a) Overload: Every hit increases the overload number by 1/2 the damage inflicted. Power Fields and Pen > 10 increases it by the full damage amount.
3b) Decreasing Protection: Same as above, but each hit removes from the protection number instead. Maybe have a minimum protection rating for each field.
3c) Limited number of hits: Each field can only absorb so many hits in a round. Maybe the tens digit of the Field Rating.
3d) Multiple Sources: Like Void shields, any of the above but they only count from a single source. Exactly like void shields. The negative is that not everyone uses multiple attacks.
4) Dark Heresy: Assign each field a #d10 and use the dark heresy versions that just add to AP. (Courtesy Umbranus and Errant)
5) Double Trouble: Doubles let the attack through. 11, 22, 33, 44, 55, 66, 77, etc. The field doesn't fail, but the attack gets through and does damage.
I'm leaning the most towards 3b and setting a minimum between 20 and 35. It will encourage people to still dodge and take cover, and it won't completely strip the protection away, but as the field absorbs more and more, it gets weaker and weaker.
As I said above, please make comments and further additions.