Hope this reply helps?
If you are referring to Bitshares/Steem as consortium blockchains, then I would say that delegates are a solution to scalability, high performance and minimal cost of sustaining the network and processing transactions. Or are you trying to say that it is actually an attempt to achieve finality faster?
Your much appreciated question expectedly exhibits grave lack of understanding of some of the technological and political-economic issues. You’re not alone, as most people are similarly clueless. You’re not mentioning in your analysis the absolute importance of resilience and trustlessness. If we simply wanted to replicate our trust in a corporation such as Visa, then why bother? My blog already contains some explanation and links to more explanation about the political clusterfuck of voting and ramifications thereof as it pertains to sustained and Internet scalable resilience and trustlessness.
A corporation such as Visa whose shareholders vote for the directors of corporation, is an analogy for DPoS. Our governments are like a giant corporation which we will have a stake in and vote for politicians to steal from the collective for us[for the elite who manipulate us like sheep]. IOW, voting ≠ resilience & trustlessness. A possible definition for insanity is doing the same ignorant thing repeatedly and wondering why always get the same undesirable result in every instance. Unfortunately humans don’t really pay attention to history and easy forget over long time horizons that they’re repeating the same stupid paradigms.
I will not answer the first part of your comment now, because it really requires several blogs in order to sufficiently cover all the issues in exhaustive details with examples. My friendly suggestion is for you to read all of the discussion I linked for you above to get some initial (but insufficient) explanation.
I find this post very technical, but I think I understand something of what you mean. What do you think of Steems runner-up-witnesses?
I added the following to my blog to try to give naive readers some more insight into how much they do not know and which explains why having a backup set of delegates (aka witnesses) is irrelevant:
The naive reader (and the neophyte Dan Larimer!) will be confused as to why the non-responding delegates can’t be replaced by a stake election. There are three reasons why such a naive assumption is mathematically impossible:
If the liveness threshold has been exceeded, then any blocks which confirm the result of a stake election aren’t objectively final due to the math of Byzantine fault tolerant agreement (consensus) as detailed below, i.e. an unbounded number of conflicting forks can be created. If instead record the results of the election offchain, then we’re executing a (potentially contentious) hardfork, thus not avoiding what Dan alleged that DPoS avoids! I sort of expect readers to work this out in their head, but I guess I realize I need to be more explicit in addressing all the various incorrect logic that naive minds can wander to.
Who is voting over and over for non-responding delegates (unbounded into the future) may not be objectively knowable nor defeatable as explained in the Permissioned liveness = overlords section of this blog.
If more than ²/₃ of the delegates are colluding, it’s mathematically impossible to determine which delegates are non-responding, because they can produce an unbounded number of forks wherein in each fork a different set of them are non-responding, yet all of the forks exceed the liveness threshold. Thus it is ambiguous which are non-responding, because they all are! Yet in any given fork, only some are; thus, it’s not objectively provable which are non-responding. The naive non-mathematical mind can’t grok that.
What we realize above is an underlying generative essence which is that Byzantine fault tolerance is a relativity problem and when the mathematical thresholds are exceeded, then all objectivity is lost. Stake voting can’t overcome that mathematical generative essence.