Don’t ever expect DW to make sensible balancing decisions.
Anyway, I’ll give my thoughts on the topic.
Sigurd’s skill 1 is actually really good. Most 100% crit buffs in this game last 1 turn (except Emiya Archer who got it for 3 turns but that’s only justified because of Emiya’s awkward deck hampering his damage potential), Sigurd got it for 3 hits turn-based it is quite easy to maximise the use of this crit skill. I would love for old Li to have a hit-based crit skill too but DW says nah.
Skill 2 is a Mana Burst on prolonged cooldown because of a little guts skill. Yea it is a poor trade-off most of the time, but at the same time long cooldown does not impact Sigurd that much. Sigurd’s an aggressive servant who’s designed to pump out a ton of damage quickly and kill the enemy fast, if you are dragging on the fight long enough for steroid cooldowns to matter significantly Sigurd’s no longer the ideal point man for you team in the first place.
Skill 3 is shite. It is just shite, no other way to put it.
Despite skill 3 being basically a dead skill most of the time, Sigurd still handles his intended role well (i.e. pump out a ton of damage). For people saying ‘but muh break bars’ I should point out because of Sigurd’s high damage ceiling he’s a favourite among TA-ers dismantling multi-bar CQs in minimum turn. I won’t go into it too deeply but Sigurd’s TA records speak for itself.
A TA-er on my FL already has a L100 2k Fou NP5 Sigurd.
Sigurd’s real problem isn’t skill 3, his problem is something shared with all gold ST Sabers in the form of a pudgy 3 star Roman. Fixing skill 3 is easy, that super-Roman disrupting game balance has no easy solution.