I'd describe BOBs as the engine room of the Orc team. They do all the heavy lifting on the LOS which provides the platform from which the blitzers operate. Without BOBs to back them up Orc teams just don't have the oomph to win bash wars or effectively channel flair teams where they want.
The problem with BOBs, which is common to other low AG S4 unskilled players, is that they skill up very slowly. Lack of Block means they aren't reliable hitters. So you tend to rely more on MVPs and the lucky cas to get a skill until they've got the crucial accelerants.
My rule of thumb is that on average an unskilled BOB will gain about 1/2 SPP per game. That is almost all MVP! So an obvious thing to do is to give them "SPP accelerant" skills to help them develop faster. As a blocker the obvious candidates are Mighty Blow and Block. Mighty Blow roughly doubles the number of casualties caused, whilst Block makes you more reliable blocker. So even though Mighty Blow is much more effective at getting cas when blocking you don't use it as much because the BOB still isn't that reliable - so you are hitting at the end of the turn - and lack of block makes him easier to put on the floor. From a team perspective Block is better because you don't use as many rerolls or cause as many turnovers. So I think they are roughly even - doubling the number of SPPs gained to 1. Take Block first because of the turnovers!
A lot of coaches will read that paragraph above and decide that the best progression then for BOBs is Block & Migthy Blow (which seems to be worth about 2 SPPs per game on average). That's a perfectly valid option too for those who want a "Killer" emphasis. Doing so puts the emphasis on getting Guard on the blitzers - or giving up Guard since you don't feel that there is much competition in the strength war.
However the best skills for an individual player are not necessarily those for the team. A classic example of that is kick. Absolutely no benefit to the player with the skill - however a huge benefit to the team. For BOBs this team accellerant skill is Guard. Why is guard so good for BOBs?
- Guard is best in the thick of the melee - which is where BOBs spend their time
- Guard is best on players you don't mind getting hit. S4 & Av9 means they are tough.
- Guard is best on players who are hard to get out of the way - S4 again makes a big difference.
My experience tells me that against other Bash teams Guard is a massively more useful skill than Block or Mighty Blow - and Guard on BOBs is generally more useful than on the Blitzers because they are big & strong so harder to move and happier standing next to opposition players. Against flair teams Guard tends not to be as useful, since they can dance away. However the solid line that multiple guarding BOBs provides can allow you to force them to go the way you want - and on offence is a pretty unstoppable cage. Block probably gives a little bit more but not much and in most leagues bash teams are more common than flair teams.
My rule of thumb for BOBs is take Guard first, unless another BOB already has Block. In which case take Block. So when you first BOB makes it 16 SPPs and gets Block to compliment his Guard, then any BOB takes Block next. The reason for this is that once you have Block BOBs you will naturally want to block with them first. So you'll find the number of blocks made by Block-less BOBs dwindling, so they never catch up. When you have Block/Guard and Block BOBs you'll naturally end up using the Guards to assist more - so the lower skilled Block players will make more hits and get more Cas.
After Guard & Block, Mighty Blow & Stand Firm are both really good skills. Grab might creep in too, particuarly if you are having trouble with teams with many sidesteppers.
Generally speaking I think there are no better skills than Guard & Block for the first two slots, other than +ST. AG is a waste on a AG2 player anyway and +MA/+Av don't give a lot compared to Block/Guard. Doubles are also comparitively poor. That's not to say don't take them but that taking them probably means you've got a worse player for a long time as none of those increases help improve the SPP rate.
However once up to the 3rd skill the alternatives become more interesting. 6,4s are full of options. Av10 can be nice, particularlly in a league without any Claw. However I'd often take +MA instead as being a bit faster makes a huge difference for keeping up with the cage and providing more mobile assisting/blitzing opportunities.
Doubles have a couple of competitive candidates. Dodge, Diving Tackle and Jump Up. Dodge is good because players with tackle tend to be designed to hunt catchers rather than S4 blockers. The Block/Dodge/Guard/Stand Firm combination is about as annoying as you can get.
Diving Tackle is excellent because it makes the BOBs much better at pinning opposing players. Even Elves with dodge won't want to run away early in the turn because of the 1/4 chance of a turnover - meaning you are more likely to get chances to hit.
Jump Up is also worth a mention since it also works well with Stand Firm and helps compensate for the low speed. If you want to develop a real killer BOB then Jump Up makes Piling On a much more palatable option.
That said, ignoring the doubles & stats is okay since you probably end up with a player of roughly equivalent value anyway - and 10k less to TV.
So, all in all BOBs are a crucial element in any successful Orc team and are blessed in that their normal skill access gives them everything they really want or need. Take them all and skill them up as fast as you can. In games you are dominating use touchbacks or hand offs to get the ball to the BOB who most need the SPPs!