I'm sure the Votann index will be fine but the selection of things we were shown was not well calibrated to hype existing Votann players
The Sisters preview is a good contrast. Sisters have been a great army ever since their (modern) release but their most competitive builds in 9th revolved around Bloody Rose and Repentia in particular, and it's pretty obvious that is not going to be well supported in the index. But what we were shown makes the Martyred Lady game plan look great - it's solid in 9th already but the synergies in 10th are readily apparent even with just a few key pieces.
Votann mostly shows how their shooting is pound-for-pound weaker than 9th (and to be fair, in 9th it's extremely good) without clearly articulating the alternate game plan. Judgement Tokens in 9th feel extremely powerful and you have a number of ways of handing them out - in 10th combined with army-wide lower ballistic skill they feel like work you need to do to come back up to par (similarly to how Tau players sometimes feel about Markerlights) but it's not clear where they come from now.
Votann players probably are sleeping on how good an army-wide Toughness increase is (I felt it was extremely impactful for Orks in 9th), but it has an amusing bit of anti-synergy in that Votann kind of want you to finish off their units and generate a judgement token, not leave a couple of battleshocked squats sitting around not accomplishing much (the exact opposite of Necrons and Sisters who would just love for you to try chipping down multiple units at once).
The version of Votann in their original book would have been an absolute nightmare, but the one that was legal for play by the time it hit was not so bad. Very good but not dominant, and a very elite feeling army after points increases - the mechanics nerfs mostly just stopped you having your cake and eating it too but your kit still felt wildly good. You just didn't have many dwarves.
It is likely the new plan calls for more dwarves. I could see a plan where you push up Berserkers in Saggitairuses and force the opponent to expose themselves and accumulate tokens to deal with them, at which point your shooting moves forward and cleans up everything with a token on it, with visible units probably attracting more tokens from the Kahl. If your points costs are moderate that sort of thing is highly plausible, it just relies on facts not in evidence in the preview
The strat is amusing because it just looks worse than the Sisters one previewed the day before. It's not - it works for units that didn't suffer casualties, so a Land Fortress can use it where an Exorcist can't - but it's more expensive and requires a token on the enemy unit. For Sisters that strat fits into the Martyred Lady game plan beautifully, for Votann it falls into the uncertainty of where the token comes from other than units dying.
I agree that Relentless Efficiency is Good, Actually. In a vacuum it doesn't look as good as Oaths of Moment but if there's a key strat or two in the Index that really get the Votann's engines going (and I have to assume there's at least one that hands out tokens) those bonus CP will look very sweet.