After two tournaments, a couple friendly games, and some serious tinkering around with my lists and models I have a few notes and tentative postulations to make regarding Saim Hann and their transition to 5th. The army appears to have the same advantages as it did in 4th: extremely high mobility, a lot of S6 weaponry, and very resilient main battle tanks very effective at anti-armor and anti-infantry. It also has pretty much the same weaknesses: low model count and very weak in assault.
I’ve found a circle and inundate strategy to be most effective with my own list. If the opponent deploys in a small concentrated area, they can be quickly surrounded and blown into oblivion. If the opponent deploys in a long battle line on his table edge, the Saim Hann should match their deployment but quickly redeploy to attack whichever flank contains the enemy’s slow/static units. Splitting fire is bad, concentrating fire is good. Above all SH eldar never want to be successfully charged. If this means effective fire has to be reduced because units spend a turn maneuvering (escaping), so be it; you’ve already spent the points to gain this advantage so use them! In this regard, the most dangerous units are those that can surprise you with a fast assault, e.g. jump troops or cavalry approaching behind cover (especially stormboyz), waaghing orks jumping from trukks. If outflankers or rear-guard attackers (wolf scouts) are around, it might be worth it to sweep your bikes and tanks into the middle of the table and go full offense.
Since ICs can be picked out as a target in 5th, Farseers should either be camped out in complete safety behind solid cover or join a jetbike squad on the move. Joining a bike squad with an embolden warlock allows him to reroll failed psychic tests (it’s a leadership test!) and grants his own Ld 10 for them to use. Obviously if you have to sacrifice a bike squad to an enemy, choose one without a Farseer attached. I’m still figuring out which powers are the best for my own list, though I would probably never use eldritch storm.
Vectored engines are practically useless on anything but transports and even then their value is questionable. Skimmers will only wreck from an immobilized result after moving flat out (or if part of a squadron, more about that later), but in order to fire you have to move less than flat out anyway (0-12”). Thus with Prisms you will very rarely be moving at such high speeds, and even then they will get a 4+ cover save out in the open. True, transports might be going that fast, but the new wrecked vehicle effects on passengers are pretty much negligible, and with fleet the squad can probably get where they’re going the next turn anyway. Star engines still seem worthwhile though, giving SH the best mobility in the galaxy short of deep-striking.
Now on the subject of Vypers. Vypers ostensibly get worse in 5th, because fast skimmers can be penetrated no matter how fast they move, and open-topped means a destroyed result at least half of the time. True, immobilized results no longer automatically destroy them so long as they move less than 12”, but the new squadron rules state that immobilized results count as destroyed. Because of this (not to mention the high price of the unit), it seems like a good idea to break them up into individual units of one Vyper each. It’s really too bad I won’t be able to guide them all at once anymore, but they’ll still be able to contest objectives at the last second and give a little fire support to boot. To compensate for their greater vulnerability in 5th, I’m giving them holofields and keeping them obscured as much as possible. Holofields will reduce their vulnerability to a destroyed result by at least half. Since they’ll be behind cover and targets will usually get a cover save from them, I’m considering giving them scatter lasers instead of starcannons. Same strength, more shots. I could switch them out for warp spiders or the like, but they’re such a big part of the SH flavor I can’t bear to let them go.