Come-from-Beyond, I think some of that may be outdated, describing an older version of DPOS. Specifically,
- At all times no delegate may have more than 2% of the vote. Any transaction or block that would give a delegate more than 2% of the vote is to be rejected.
I could be somehow mistaken,
but this does not seem to be the case.
I interpreted 2% vote limit as a way to force stakeholders to vote for at least 50 delegates. If it means that none of the delegates is allowed to generate more than 2% of blocks then the attack above will lead to exclusion of 33% of legit delegates and 33% of rogue delegates from block generation process (because they can't sign another chain if they already signed the attacker's one). And this leads to worse consequences. The attackers may get more than 33% of slots in the next top 66 delegates that will replace current leaders (assuming that it's easier to be in top 200 than in top 100).
Edit:
Such "rating grinding" attack (when rogue delegates commit suicide and force some honest delegates to be excluded too) is a neat feature for attackers. In this case no need to have 33 delegates, N attackers can be fired together with N+M honest delegates (the same way as 51% attack can be conducted with less than 51% of hashing power). Repeating this process the attackers may slowly increase percentage of occupied slots... Note that I don't know BitShares internals very well, if someone explained the process of firing of delegates it would help to assess how feasible "rating grinding" is.